two version of R2R are hereHEADmaster

12 files changed, 5702 insertions, 0 deletions

diff --git a/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/__init__.py b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/__init__.py
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/__init__.py
diff --git a/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_adjlist.py b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_adjlist.py
new file mode 100644
index 00000000..f2218eba
--- /dev/null
+++ b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_adjlist.py
@@ -0,0 +1,262 @@
+"""
+Unit tests for adjlist.
+"""
+
+import io
+
+import pytest
+
+import networkx as nx
+from networkx.utils import edges_equal, graphs_equal, nodes_equal
+
+
+class TestAdjlist:
+    @classmethod
+    def setup_class(cls):
+        cls.G = nx.Graph(name="test")
+        e = [("a", "b"), ("b", "c"), ("c", "d"), ("d", "e"), ("e", "f"), ("a", "f")]
+        cls.G.add_edges_from(e)
+        cls.G.add_node("g")
+        cls.DG = nx.DiGraph(cls.G)
+        cls.XG = nx.MultiGraph()
+        cls.XG.add_weighted_edges_from([(1, 2, 5), (1, 2, 5), (1, 2, 1), (3, 3, 42)])
+        cls.XDG = nx.MultiDiGraph(cls.XG)
+
+    def test_read_multiline_adjlist_1(self):
+        # Unit test for https://networkx.lanl.gov/trac/ticket/252
+        s = b"""# comment line
+1 2
+# comment line
+2
+3
+"""
+        bytesIO = io.BytesIO(s)
+        G = nx.read_multiline_adjlist(bytesIO)
+        adj = {"1": {"3": {}, "2": {}}, "3": {"1": {}}, "2": {"1": {}}}
+        assert graphs_equal(G, nx.Graph(adj))
+
+    def test_unicode(self, tmp_path):
+        G = nx.Graph()
+        name1 = chr(2344) + chr(123) + chr(6543)
+        name2 = chr(5543) + chr(1543) + chr(324)
+        G.add_edge(name1, "Radiohead", **{name2: 3})
+
+        fname = tmp_path / "adjlist.txt"
+        nx.write_multiline_adjlist(G, fname)
+        H = nx.read_multiline_adjlist(fname)
+        assert graphs_equal(G, H)
+
+    def test_latin1_err(self, tmp_path):
+        G = nx.Graph()
+        name1 = chr(2344) + chr(123) + chr(6543)
+        name2 = chr(5543) + chr(1543) + chr(324)
+        G.add_edge(name1, "Radiohead", **{name2: 3})
+        fname = tmp_path / "adjlist.txt"
+        with pytest.raises(UnicodeEncodeError):
+            nx.write_multiline_adjlist(G, fname, encoding="latin-1")
+
+    def test_latin1(self, tmp_path):
+        G = nx.Graph()
+        name1 = "Bj" + chr(246) + "rk"
+        name2 = chr(220) + "ber"
+        G.add_edge(name1, "Radiohead", **{name2: 3})
+        fname = tmp_path / "adjlist.txt"
+        nx.write_multiline_adjlist(G, fname, encoding="latin-1")
+        H = nx.read_multiline_adjlist(fname, encoding="latin-1")
+        assert graphs_equal(G, H)
+
+    def test_parse_adjlist(self):
+        lines = ["1 2 5", "2 3 4", "3 5", "4", "5"]
+        nx.parse_adjlist(lines, nodetype=int)  # smoke test
+        with pytest.raises(TypeError):
+            nx.parse_adjlist(lines, nodetype="int")
+        lines = ["1 2 5", "2 b", "c"]
+        with pytest.raises(TypeError):
+            nx.parse_adjlist(lines, nodetype=int)
+
+    def test_adjlist_graph(self, tmp_path):
+        G = self.G
+        fname = tmp_path / "adjlist.txt"
+        nx.write_adjlist(G, fname)
+        H = nx.read_adjlist(fname)
+        H2 = nx.read_adjlist(fname)
+        assert H is not H2  # they should be different graphs
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_adjlist_digraph(self, tmp_path):
+        G = self.DG
+        fname = tmp_path / "adjlist.txt"
+        nx.write_adjlist(G, fname)
+        H = nx.read_adjlist(fname, create_using=nx.DiGraph())
+        H2 = nx.read_adjlist(fname, create_using=nx.DiGraph())
+        assert H is not H2  # they should be different graphs
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_adjlist_integers(self, tmp_path):
+        fname = tmp_path / "adjlist.txt"
+        G = nx.convert_node_labels_to_integers(self.G)
+        nx.write_adjlist(G, fname)
+        H = nx.read_adjlist(fname, nodetype=int)
+        H2 = nx.read_adjlist(fname, nodetype=int)
+        assert H is not H2  # they should be different graphs
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_adjlist_multigraph(self, tmp_path):
+        G = self.XG
+        fname = tmp_path / "adjlist.txt"
+        nx.write_adjlist(G, fname)
+        H = nx.read_adjlist(fname, nodetype=int, create_using=nx.MultiGraph())
+        H2 = nx.read_adjlist(fname, nodetype=int, create_using=nx.MultiGraph())
+        assert H is not H2  # they should be different graphs
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_adjlist_multidigraph(self, tmp_path):
+        G = self.XDG
+        fname = tmp_path / "adjlist.txt"
+        nx.write_adjlist(G, fname)
+        H = nx.read_adjlist(fname, nodetype=int, create_using=nx.MultiDiGraph())
+        H2 = nx.read_adjlist(fname, nodetype=int, create_using=nx.MultiDiGraph())
+        assert H is not H2  # they should be different graphs
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_adjlist_delimiter(self):
+        fh = io.BytesIO()
+        G = nx.path_graph(3)
+        nx.write_adjlist(G, fh, delimiter=":")
+        fh.seek(0)
+        H = nx.read_adjlist(fh, nodetype=int, delimiter=":")
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+
+class TestMultilineAdjlist:
+    @classmethod
+    def setup_class(cls):
+        cls.G = nx.Graph(name="test")
+        e = [("a", "b"), ("b", "c"), ("c", "d"), ("d", "e"), ("e", "f"), ("a", "f")]
+        cls.G.add_edges_from(e)
+        cls.G.add_node("g")
+        cls.DG = nx.DiGraph(cls.G)
+        cls.DG.remove_edge("b", "a")
+        cls.DG.remove_edge("b", "c")
+        cls.XG = nx.MultiGraph()
+        cls.XG.add_weighted_edges_from([(1, 2, 5), (1, 2, 5), (1, 2, 1), (3, 3, 42)])
+        cls.XDG = nx.MultiDiGraph(cls.XG)
+
+    def test_parse_multiline_adjlist(self):
+        lines = [
+            "1 2",
+            "b {'weight':3, 'name': 'Frodo'}",
+            "c {}",
+            "d 1",
+            "e {'weight':6, 'name': 'Saruman'}",
+        ]
+        nx.parse_multiline_adjlist(iter(lines))  # smoke test
+        with pytest.raises(TypeError):
+            nx.parse_multiline_adjlist(iter(lines), nodetype=int)
+        nx.parse_multiline_adjlist(iter(lines), edgetype=str)  # smoke test
+        with pytest.raises(TypeError):
+            nx.parse_multiline_adjlist(iter(lines), nodetype=int)
+        lines = ["1 a"]
+        with pytest.raises(TypeError):
+            nx.parse_multiline_adjlist(iter(lines))
+        lines = ["a 2"]
+        with pytest.raises(TypeError):
+            nx.parse_multiline_adjlist(iter(lines), nodetype=int)
+        lines = ["1 2"]
+        with pytest.raises(TypeError):
+            nx.parse_multiline_adjlist(iter(lines))
+        lines = ["1 2", "2 {}"]
+        with pytest.raises(TypeError):
+            nx.parse_multiline_adjlist(iter(lines))
+
+    def test_multiline_adjlist_graph(self, tmp_path):
+        G = self.G
+        fname = tmp_path / "adjlist.txt"
+        nx.write_multiline_adjlist(G, fname)
+        H = nx.read_multiline_adjlist(fname)
+        H2 = nx.read_multiline_adjlist(fname)
+        assert H is not H2  # they should be different graphs
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_multiline_adjlist_digraph(self, tmp_path):
+        G = self.DG
+        fname = tmp_path / "adjlist.txt"
+        nx.write_multiline_adjlist(G, fname)
+        H = nx.read_multiline_adjlist(fname, create_using=nx.DiGraph())
+        H2 = nx.read_multiline_adjlist(fname, create_using=nx.DiGraph())
+        assert H is not H2  # they should be different graphs
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_multiline_adjlist_integers(self, tmp_path):
+        fname = tmp_path / "adjlist.txt"
+        G = nx.convert_node_labels_to_integers(self.G)
+        nx.write_multiline_adjlist(G, fname)
+        H = nx.read_multiline_adjlist(fname, nodetype=int)
+        H2 = nx.read_multiline_adjlist(fname, nodetype=int)
+        assert H is not H2  # they should be different graphs
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_multiline_adjlist_multigraph(self, tmp_path):
+        G = self.XG
+        fname = tmp_path / "adjlist.txt"
+        nx.write_multiline_adjlist(G, fname)
+        H = nx.read_multiline_adjlist(fname, nodetype=int, create_using=nx.MultiGraph())
+        H2 = nx.read_multiline_adjlist(
+            fname, nodetype=int, create_using=nx.MultiGraph()
+        )
+        assert H is not H2  # they should be different graphs
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_multiline_adjlist_multidigraph(self, tmp_path):
+        G = self.XDG
+        fname = tmp_path / "adjlist.txt"
+        nx.write_multiline_adjlist(G, fname)
+        H = nx.read_multiline_adjlist(
+            fname, nodetype=int, create_using=nx.MultiDiGraph()
+        )
+        H2 = nx.read_multiline_adjlist(
+            fname, nodetype=int, create_using=nx.MultiDiGraph()
+        )
+        assert H is not H2  # they should be different graphs
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_multiline_adjlist_delimiter(self):
+        fh = io.BytesIO()
+        G = nx.path_graph(3)
+        nx.write_multiline_adjlist(G, fh, delimiter=":")
+        fh.seek(0)
+        H = nx.read_multiline_adjlist(fh, nodetype=int, delimiter=":")
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+
+@pytest.mark.parametrize(
+    ("lines", "delim"),
+    (
+        (["1 2 5", "2 3 4", "3 5", "4", "5"], None),  # No extra whitespace
+        (["1\t2\t5", "2\t3\t4", "3\t5", "4", "5"], "\t"),  # tab-delimited
+        (
+            ["1\t2\t5", "2\t3\t4", "3\t5\t", "4\t", "5"],
+            "\t",
+        ),  # tab-delimited, extra delims
+        (
+            ["1\t2\t5", "2\t3\t4", "3\t5\t\t\n", "4\t", "5"],
+            "\t",
+        ),  # extra delim+newlines
+    ),
+)
+def test_adjlist_rstrip_parsing(lines, delim):
+    """Regression test related to gh-7465"""
+    expected = nx.Graph([(1, 2), (1, 5), (2, 3), (2, 4), (3, 5)])
+    nx.utils.graphs_equal(nx.parse_adjlist(lines, delimiter=delim), expected)
diff --git a/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_edgelist.py b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_edgelist.py
new file mode 100644
index 00000000..fe58b3b7
--- /dev/null
+++ b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_edgelist.py
@@ -0,0 +1,314 @@
+"""
+Unit tests for edgelists.
+"""
+
+import io
+import textwrap
+
+import pytest
+
+import networkx as nx
+from networkx.utils import edges_equal, graphs_equal, nodes_equal
+
+edges_no_data = textwrap.dedent(
+    """
+    # comment line
+    1 2
+    # comment line
+    2 3
+    """
+)
+
+
+edges_with_values = textwrap.dedent(
+    """
+    # comment line
+    1 2 2.0
+    # comment line
+    2 3 3.0
+    """
+)
+
+
+edges_with_weight = textwrap.dedent(
+    """
+    # comment line
+    1 2 {'weight':2.0}
+    # comment line
+    2 3 {'weight':3.0}
+    """
+)
+
+
+edges_with_multiple_attrs = textwrap.dedent(
+    """
+    # comment line
+    1 2 {'weight':2.0, 'color':'green'}
+    # comment line
+    2 3 {'weight':3.0, 'color':'red'}
+    """
+)
+
+
+edges_with_multiple_attrs_csv = textwrap.dedent(
+    """
+    # comment line
+    1, 2, {'weight':2.0, 'color':'green'}
+    # comment line
+    2, 3, {'weight':3.0, 'color':'red'}
+    """
+)
+
+
+_expected_edges_weights = [(1, 2, {"weight": 2.0}), (2, 3, {"weight": 3.0})]
+_expected_edges_multiattr = [
+    (1, 2, {"weight": 2.0, "color": "green"}),
+    (2, 3, {"weight": 3.0, "color": "red"}),
+]
+
+
+@pytest.mark.parametrize(
+    ("data", "extra_kwargs"),
+    (
+        (edges_no_data, {}),
+        (edges_with_values, {}),
+        (edges_with_weight, {}),
+        (edges_with_multiple_attrs, {}),
+        (edges_with_multiple_attrs_csv, {"delimiter": ","}),
+    ),
+)
+def test_read_edgelist_no_data(data, extra_kwargs):
+    bytesIO = io.BytesIO(data.encode("utf-8"))
+    G = nx.read_edgelist(bytesIO, nodetype=int, data=False, **extra_kwargs)
+    assert edges_equal(G.edges(), [(1, 2), (2, 3)])
+
+
+def test_read_weighted_edgelist():
+    bytesIO = io.BytesIO(edges_with_values.encode("utf-8"))
+    G = nx.read_weighted_edgelist(bytesIO, nodetype=int)
+    assert edges_equal(G.edges(data=True), _expected_edges_weights)
+
+
+@pytest.mark.parametrize(
+    ("data", "extra_kwargs", "expected"),
+    (
+        (edges_with_weight, {}, _expected_edges_weights),
+        (edges_with_multiple_attrs, {}, _expected_edges_multiattr),
+        (edges_with_multiple_attrs_csv, {"delimiter": ","}, _expected_edges_multiattr),
+    ),
+)
+def test_read_edgelist_with_data(data, extra_kwargs, expected):
+    bytesIO = io.BytesIO(data.encode("utf-8"))
+    G = nx.read_edgelist(bytesIO, nodetype=int, **extra_kwargs)
+    assert edges_equal(G.edges(data=True), expected)
+
+
+@pytest.fixture
+def example_graph():
+    G = nx.Graph()
+    G.add_weighted_edges_from([(1, 2, 3.0), (2, 3, 27.0), (3, 4, 3.0)])
+    return G
+
+
+def test_parse_edgelist_no_data(example_graph):
+    G = example_graph
+    H = nx.parse_edgelist(["1 2", "2 3", "3 4"], nodetype=int)
+    assert nodes_equal(G.nodes, H.nodes)
+    assert edges_equal(G.edges, H.edges)
+
+
+def test_parse_edgelist_with_data_dict(example_graph):
+    G = example_graph
+    H = nx.parse_edgelist(
+        ["1 2 {'weight': 3}", "2 3 {'weight': 27}", "3 4 {'weight': 3.0}"], nodetype=int
+    )
+    assert nodes_equal(G.nodes, H.nodes)
+    assert edges_equal(G.edges(data=True), H.edges(data=True))
+
+
+def test_parse_edgelist_with_data_list(example_graph):
+    G = example_graph
+    H = nx.parse_edgelist(
+        ["1 2 3", "2 3 27", "3 4 3.0"], nodetype=int, data=(("weight", float),)
+    )
+    assert nodes_equal(G.nodes, H.nodes)
+    assert edges_equal(G.edges(data=True), H.edges(data=True))
+
+
+def test_parse_edgelist():
+    # ignore lines with less than 2 nodes
+    lines = ["1;2", "2 3", "3 4"]
+    G = nx.parse_edgelist(lines, nodetype=int)
+    assert list(G.edges()) == [(2, 3), (3, 4)]
+    # unknown nodetype
+    with pytest.raises(TypeError, match="Failed to convert nodes"):
+        lines = ["1 2", "2 3", "3 4"]
+        nx.parse_edgelist(lines, nodetype="nope")
+    # lines have invalid edge format
+    with pytest.raises(TypeError, match="Failed to convert edge data"):
+        lines = ["1 2 3", "2 3", "3 4"]
+        nx.parse_edgelist(lines, nodetype=int)
+    # edge data and data_keys not the same length
+    with pytest.raises(IndexError, match="not the same length"):
+        lines = ["1 2 3", "2 3 27", "3 4 3.0"]
+        nx.parse_edgelist(
+            lines, nodetype=int, data=(("weight", float), ("capacity", int))
+        )
+    # edge data can't be converted to edge type
+    with pytest.raises(TypeError, match="Failed to convert"):
+        lines = ["1 2 't1'", "2 3 't3'", "3 4 't3'"]
+        nx.parse_edgelist(lines, nodetype=int, data=(("weight", float),))
+
+
+def test_comments_None():
+    edgelist = ["node#1 node#2", "node#2 node#3"]
+    # comments=None supported to ignore all comment characters
+    G = nx.parse_edgelist(edgelist, comments=None)
+    H = nx.Graph([e.split(" ") for e in edgelist])
+    assert edges_equal(G.edges, H.edges)
+
+
+class TestEdgelist:
+    @classmethod
+    def setup_class(cls):
+        cls.G = nx.Graph(name="test")
+        e = [("a", "b"), ("b", "c"), ("c", "d"), ("d", "e"), ("e", "f"), ("a", "f")]
+        cls.G.add_edges_from(e)
+        cls.G.add_node("g")
+        cls.DG = nx.DiGraph(cls.G)
+        cls.XG = nx.MultiGraph()
+        cls.XG.add_weighted_edges_from([(1, 2, 5), (1, 2, 5), (1, 2, 1), (3, 3, 42)])
+        cls.XDG = nx.MultiDiGraph(cls.XG)
+
+    def test_write_edgelist_1(self):
+        fh = io.BytesIO()
+        G = nx.Graph()
+        G.add_edges_from([(1, 2), (2, 3)])
+        nx.write_edgelist(G, fh, data=False)
+        fh.seek(0)
+        assert fh.read() == b"1 2\n2 3\n"
+
+    def test_write_edgelist_2(self):
+        fh = io.BytesIO()
+        G = nx.Graph()
+        G.add_edges_from([(1, 2), (2, 3)])
+        nx.write_edgelist(G, fh, data=True)
+        fh.seek(0)
+        assert fh.read() == b"1 2 {}\n2 3 {}\n"
+
+    def test_write_edgelist_3(self):
+        fh = io.BytesIO()
+        G = nx.Graph()
+        G.add_edge(1, 2, weight=2.0)
+        G.add_edge(2, 3, weight=3.0)
+        nx.write_edgelist(G, fh, data=True)
+        fh.seek(0)
+        assert fh.read() == b"1 2 {'weight': 2.0}\n2 3 {'weight': 3.0}\n"
+
+    def test_write_edgelist_4(self):
+        fh = io.BytesIO()
+        G = nx.Graph()
+        G.add_edge(1, 2, weight=2.0)
+        G.add_edge(2, 3, weight=3.0)
+        nx.write_edgelist(G, fh, data=[("weight")])
+        fh.seek(0)
+        assert fh.read() == b"1 2 2.0\n2 3 3.0\n"
+
+    def test_unicode(self, tmp_path):
+        G = nx.Graph()
+        name1 = chr(2344) + chr(123) + chr(6543)
+        name2 = chr(5543) + chr(1543) + chr(324)
+        G.add_edge(name1, "Radiohead", **{name2: 3})
+        fname = tmp_path / "el.txt"
+        nx.write_edgelist(G, fname)
+        H = nx.read_edgelist(fname)
+        assert graphs_equal(G, H)
+
+    def test_latin1_issue(self, tmp_path):
+        G = nx.Graph()
+        name1 = chr(2344) + chr(123) + chr(6543)
+        name2 = chr(5543) + chr(1543) + chr(324)
+        G.add_edge(name1, "Radiohead", **{name2: 3})
+        fname = tmp_path / "el.txt"
+        with pytest.raises(UnicodeEncodeError):
+            nx.write_edgelist(G, fname, encoding="latin-1")
+
+    def test_latin1(self, tmp_path):
+        G = nx.Graph()
+        name1 = "Bj" + chr(246) + "rk"
+        name2 = chr(220) + "ber"
+        G.add_edge(name1, "Radiohead", **{name2: 3})
+        fname = tmp_path / "el.txt"
+
+        nx.write_edgelist(G, fname, encoding="latin-1")
+        H = nx.read_edgelist(fname, encoding="latin-1")
+        assert graphs_equal(G, H)
+
+    def test_edgelist_graph(self, tmp_path):
+        G = self.G
+        fname = tmp_path / "el.txt"
+        nx.write_edgelist(G, fname)
+        H = nx.read_edgelist(fname)
+        H2 = nx.read_edgelist(fname)
+        assert H is not H2  # they should be different graphs
+        G.remove_node("g")  # isolated nodes are not written in edgelist
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_edgelist_digraph(self, tmp_path):
+        G = self.DG
+        fname = tmp_path / "el.txt"
+        nx.write_edgelist(G, fname)
+        H = nx.read_edgelist(fname, create_using=nx.DiGraph())
+        H2 = nx.read_edgelist(fname, create_using=nx.DiGraph())
+        assert H is not H2  # they should be different graphs
+        G.remove_node("g")  # isolated nodes are not written in edgelist
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_edgelist_integers(self, tmp_path):
+        G = nx.convert_node_labels_to_integers(self.G)
+        fname = tmp_path / "el.txt"
+        nx.write_edgelist(G, fname)
+        H = nx.read_edgelist(fname, nodetype=int)
+        # isolated nodes are not written in edgelist
+        G.remove_nodes_from(list(nx.isolates(G)))
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_edgelist_multigraph(self, tmp_path):
+        G = self.XG
+        fname = tmp_path / "el.txt"
+        nx.write_edgelist(G, fname)
+        H = nx.read_edgelist(fname, nodetype=int, create_using=nx.MultiGraph())
+        H2 = nx.read_edgelist(fname, nodetype=int, create_using=nx.MultiGraph())
+        assert H is not H2  # they should be different graphs
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+    def test_edgelist_multidigraph(self, tmp_path):
+        G = self.XDG
+        fname = tmp_path / "el.txt"
+        nx.write_edgelist(G, fname)
+        H = nx.read_edgelist(fname, nodetype=int, create_using=nx.MultiDiGraph())
+        H2 = nx.read_edgelist(fname, nodetype=int, create_using=nx.MultiDiGraph())
+        assert H is not H2  # they should be different graphs
+        assert nodes_equal(list(H), list(G))
+        assert edges_equal(list(H.edges()), list(G.edges()))
+
+
+def test_edgelist_consistent_strip_handling():
+    """See gh-7462
+
+    Input when printed looks like::
+
+        1       2       3
+        2       3
+        3       4       3.0
+
+    Note the trailing \\t after the `3` in the second row, indicating an empty
+    data value.
+    """
+    s = io.StringIO("1\t2\t3\n2\t3\t\n3\t4\t3.0")
+    G = nx.parse_edgelist(s, delimiter="\t", nodetype=int, data=[("value", str)])
+    assert sorted(G.edges(data="value")) == [(1, 2, "3"), (2, 3, ""), (3, 4, "3.0")]
diff --git a/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_gexf.py b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_gexf.py
new file mode 100644
index 00000000..6ff14c99
--- /dev/null
+++ b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_gexf.py
@@ -0,0 +1,557 @@
+import io
+import time
+
+import pytest
+
+import networkx as nx
+
+
+class TestGEXF:
+    @classmethod
+    def setup_class(cls):
+        cls.simple_directed_data = """<?xml version="1.0" encoding="UTF-8"?>
+<gexf xmlns="http://www.gexf.net/1.2draft" version="1.2">
+    <graph mode="static" defaultedgetype="directed">
+        <nodes>
+            <node id="0" label="Hello" />
+            <node id="1" label="Word" />
+        </nodes>
+        <edges>
+            <edge id="0" source="0" target="1" />
+        </edges>
+    </graph>
+</gexf>
+"""
+        cls.simple_directed_graph = nx.DiGraph()
+        cls.simple_directed_graph.add_node("0", label="Hello")
+        cls.simple_directed_graph.add_node("1", label="World")
+        cls.simple_directed_graph.add_edge("0", "1", id="0")
+
+        cls.simple_directed_fh = io.BytesIO(cls.simple_directed_data.encode("UTF-8"))
+
+        cls.attribute_data = """<?xml version="1.0" encoding="UTF-8"?>\
+<gexf xmlns="http://www.gexf.net/1.2draft" xmlns:xsi="http://www.w3.\
+org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.gexf.net/\
+1.2draft http://www.gexf.net/1.2draft/gexf.xsd" version="1.2">
+  <meta lastmodifieddate="2009-03-20">
+    <creator>Gephi.org</creator>
+    <description>A Web network</description>
+  </meta>
+  <graph defaultedgetype="directed">
+    <attributes class="node">
+      <attribute id="0" title="url" type="string"/>
+      <attribute id="1" title="indegree" type="integer"/>
+      <attribute id="2" title="frog" type="boolean">
+        <default>true</default>
+      </attribute>
+    </attributes>
+    <nodes>
+      <node id="0" label="Gephi">
+        <attvalues>
+          <attvalue for="0" value="https://gephi.org"/>
+          <attvalue for="1" value="1"/>
+          <attvalue for="2" value="false"/>
+        </attvalues>
+      </node>
+      <node id="1" label="Webatlas">
+        <attvalues>
+          <attvalue for="0" value="http://webatlas.fr"/>
+          <attvalue for="1" value="2"/>
+          <attvalue for="2" value="false"/>
+        </attvalues>
+      </node>
+      <node id="2" label="RTGI">
+        <attvalues>
+          <attvalue for="0" value="http://rtgi.fr"/>
+          <attvalue for="1" value="1"/>
+          <attvalue for="2" value="true"/>
+        </attvalues>
+      </node>
+      <node id="3" label="BarabasiLab">
+        <attvalues>
+          <attvalue for="0" value="http://barabasilab.com"/>
+          <attvalue for="1" value="1"/>
+          <attvalue for="2" value="true"/>
+        </attvalues>
+      </node>
+    </nodes>
+    <edges>
+      <edge id="0" source="0" target="1" label="foo"/>
+      <edge id="1" source="0" target="2"/>
+      <edge id="2" source="1" target="0"/>
+      <edge id="3" source="2" target="1"/>
+      <edge id="4" source="0" target="3"/>
+    </edges>
+  </graph>
+</gexf>
+"""
+        cls.attribute_graph = nx.DiGraph()
+        cls.attribute_graph.graph["node_default"] = {"frog": True}
+        cls.attribute_graph.add_node(
+            "0", label="Gephi", url="https://gephi.org", indegree=1, frog=False
+        )
+        cls.attribute_graph.add_node(
+            "1", label="Webatlas", url="http://webatlas.fr", indegree=2, frog=False
+        )
+        cls.attribute_graph.add_node(
+            "2", label="RTGI", url="http://rtgi.fr", indegree=1, frog=True
+        )
+        cls.attribute_graph.add_node(
+            "3",
+            label="BarabasiLab",
+            url="http://barabasilab.com",
+            indegree=1,
+            frog=True,
+        )
+        cls.attribute_graph.add_edge("0", "1", id="0", label="foo")
+        cls.attribute_graph.add_edge("0", "2", id="1")
+        cls.attribute_graph.add_edge("1", "0", id="2")
+        cls.attribute_graph.add_edge("2", "1", id="3")
+        cls.attribute_graph.add_edge("0", "3", id="4")
+        cls.attribute_fh = io.BytesIO(cls.attribute_data.encode("UTF-8"))
+
+        cls.simple_undirected_data = """<?xml version="1.0" encoding="UTF-8"?>
+<gexf xmlns="http://www.gexf.net/1.2draft" version="1.2">
+    <graph mode="static" defaultedgetype="undirected">
+        <nodes>
+            <node id="0" label="Hello" />
+            <node id="1" label="Word" />
+        </nodes>
+        <edges>
+            <edge id="0" source="0" target="1" />
+        </edges>
+    </graph>
+</gexf>
+"""
+        cls.simple_undirected_graph = nx.Graph()
+        cls.simple_undirected_graph.add_node("0", label="Hello")
+        cls.simple_undirected_graph.add_node("1", label="World")
+        cls.simple_undirected_graph.add_edge("0", "1", id="0")
+
+        cls.simple_undirected_fh = io.BytesIO(
+            cls.simple_undirected_data.encode("UTF-8")
+        )
+
+    def test_read_simple_directed_graphml(self):
+        G = self.simple_directed_graph
+        H = nx.read_gexf(self.simple_directed_fh)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(G.edges()) == sorted(H.edges())
+        assert sorted(G.edges(data=True)) == sorted(H.edges(data=True))
+        self.simple_directed_fh.seek(0)
+
+    def test_write_read_simple_directed_graphml(self):
+        G = self.simple_directed_graph
+        fh = io.BytesIO()
+        nx.write_gexf(G, fh)
+        fh.seek(0)
+        H = nx.read_gexf(fh)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(G.edges()) == sorted(H.edges())
+        assert sorted(G.edges(data=True)) == sorted(H.edges(data=True))
+        self.simple_directed_fh.seek(0)
+
+    def test_read_simple_undirected_graphml(self):
+        G = self.simple_undirected_graph
+        H = nx.read_gexf(self.simple_undirected_fh)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(sorted(e) for e in G.edges()) == sorted(
+            sorted(e) for e in H.edges()
+        )
+        self.simple_undirected_fh.seek(0)
+
+    def test_read_attribute_graphml(self):
+        G = self.attribute_graph
+        H = nx.read_gexf(self.attribute_fh)
+        assert sorted(G.nodes(True)) == sorted(H.nodes(data=True))
+        ge = sorted(G.edges(data=True))
+        he = sorted(H.edges(data=True))
+        for a, b in zip(ge, he):
+            assert a == b
+        self.attribute_fh.seek(0)
+
+    def test_directed_edge_in_undirected(self):
+        s = """<?xml version="1.0" encoding="UTF-8"?>
+<gexf xmlns="http://www.gexf.net/1.2draft" version='1.2'>
+    <graph mode="static" defaultedgetype="undirected" name="">
+        <nodes>
+            <node id="0" label="Hello" />
+            <node id="1" label="Word" />
+        </nodes>
+        <edges>
+            <edge id="0" source="0" target="1" type="directed"/>
+        </edges>
+    </graph>
+</gexf>
+"""
+        fh = io.BytesIO(s.encode("UTF-8"))
+        pytest.raises(nx.NetworkXError, nx.read_gexf, fh)
+
+    def test_undirected_edge_in_directed(self):
+        s = """<?xml version="1.0" encoding="UTF-8"?>
+<gexf xmlns="http://www.gexf.net/1.2draft" version='1.2'>
+    <graph mode="static" defaultedgetype="directed" name="">
+        <nodes>
+            <node id="0" label="Hello" />
+            <node id="1" label="Word" />
+        </nodes>
+        <edges>
+            <edge id="0" source="0" target="1" type="undirected"/>
+        </edges>
+    </graph>
+</gexf>
+"""
+        fh = io.BytesIO(s.encode("UTF-8"))
+        pytest.raises(nx.NetworkXError, nx.read_gexf, fh)
+
+    def test_key_raises(self):
+        s = """<?xml version="1.0" encoding="UTF-8"?>
+<gexf xmlns="http://www.gexf.net/1.2draft" version='1.2'>
+    <graph mode="static" defaultedgetype="directed" name="">
+        <nodes>
+            <node id="0" label="Hello">
+              <attvalues>
+                <attvalue for='0' value='1'/>
+              </attvalues>
+            </node>
+            <node id="1" label="Word" />
+        </nodes>
+        <edges>
+            <edge id="0" source="0" target="1" type="undirected"/>
+        </edges>
+    </graph>
+</gexf>
+"""
+        fh = io.BytesIO(s.encode("UTF-8"))
+        pytest.raises(nx.NetworkXError, nx.read_gexf, fh)
+
+    def test_relabel(self):
+        s = """<?xml version="1.0" encoding="UTF-8"?>
+<gexf xmlns="http://www.gexf.net/1.2draft" version='1.2'>
+    <graph mode="static" defaultedgetype="directed" name="">
+        <nodes>
+            <node id="0" label="Hello" />
+            <node id="1" label="Word" />
+        </nodes>
+        <edges>
+            <edge id="0" source="0" target="1"/>
+        </edges>
+    </graph>
+</gexf>
+"""
+        fh = io.BytesIO(s.encode("UTF-8"))
+        G = nx.read_gexf(fh, relabel=True)
+        assert sorted(G.nodes()) == ["Hello", "Word"]
+
+    def test_default_attribute(self):
+        G = nx.Graph()
+        G.add_node(1, label="1", color="green")
+        nx.add_path(G, [0, 1, 2, 3])
+        G.add_edge(1, 2, foo=3)
+        G.graph["node_default"] = {"color": "yellow"}
+        G.graph["edge_default"] = {"foo": 7}
+        fh = io.BytesIO()
+        nx.write_gexf(G, fh)
+        fh.seek(0)
+        H = nx.read_gexf(fh, node_type=int)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(sorted(e) for e in G.edges()) == sorted(
+            sorted(e) for e in H.edges()
+        )
+        # Reading a gexf graph always sets mode attribute to either
+        # 'static' or 'dynamic'. Remove the mode attribute from the
+        # read graph for the sake of comparing remaining attributes.
+        del H.graph["mode"]
+        assert G.graph == H.graph
+
+    def test_serialize_ints_to_strings(self):
+        G = nx.Graph()
+        G.add_node(1, id=7, label=77)
+        fh = io.BytesIO()
+        nx.write_gexf(G, fh)
+        fh.seek(0)
+        H = nx.read_gexf(fh, node_type=int)
+        assert list(H) == [7]
+        assert H.nodes[7]["label"] == "77"
+
+    def test_write_with_node_attributes(self):
+        # Addresses #673.
+        G = nx.Graph()
+        G.add_edges_from([(0, 1), (1, 2), (2, 3)])
+        for i in range(4):
+            G.nodes[i]["id"] = i
+            G.nodes[i]["label"] = i
+            G.nodes[i]["pid"] = i
+            G.nodes[i]["start"] = i
+            G.nodes[i]["end"] = i + 1
+
+        expected = f"""<gexf xmlns="http://www.gexf.net/1.2draft" xmlns:xsi\
+="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation=\
+"http://www.gexf.net/1.2draft http://www.gexf.net/1.2draft/\
+gexf.xsd" version="1.2">
+  <meta lastmodifieddate="{time.strftime('%Y-%m-%d')}">
+    <creator>NetworkX {nx.__version__}</creator>
+  </meta>
+  <graph defaultedgetype="undirected" mode="dynamic" name="" timeformat="long">
+    <nodes>
+      <node id="0" label="0" pid="0" start="0" end="1" />
+      <node id="1" label="1" pid="1" start="1" end="2" />
+      <node id="2" label="2" pid="2" start="2" end="3" />
+      <node id="3" label="3" pid="3" start="3" end="4" />
+    </nodes>
+    <edges>
+      <edge source="0" target="1" id="0" />
+      <edge source="1" target="2" id="1" />
+      <edge source="2" target="3" id="2" />
+    </edges>
+  </graph>
+</gexf>"""
+        obtained = "\n".join(nx.generate_gexf(G))
+        assert expected == obtained
+
+    def test_edge_id_construct(self):
+        G = nx.Graph()
+        G.add_edges_from([(0, 1, {"id": 0}), (1, 2, {"id": 2}), (2, 3)])
+
+        expected = f"""<gexf xmlns="http://www.gexf.net/1.2draft" xmlns:xsi\
+="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.\
+gexf.net/1.2draft http://www.gexf.net/1.2draft/gexf.xsd" version="1.2">
+  <meta lastmodifieddate="{time.strftime('%Y-%m-%d')}">
+    <creator>NetworkX {nx.__version__}</creator>
+  </meta>
+  <graph defaultedgetype="undirected" mode="static" name="">
+    <nodes>
+      <node id="0" label="0" />
+      <node id="1" label="1" />
+      <node id="2" label="2" />
+      <node id="3" label="3" />
+    </nodes>
+    <edges>
+      <edge source="0" target="1" id="0" />
+      <edge source="1" target="2" id="2" />
+      <edge source="2" target="3" id="1" />
+    </edges>
+  </graph>
+</gexf>"""
+
+        obtained = "\n".join(nx.generate_gexf(G))
+        assert expected == obtained
+
+    def test_numpy_type(self):
+        np = pytest.importorskip("numpy")
+        G = nx.path_graph(4)
+        nx.set_node_attributes(G, {n: n for n in np.arange(4)}, "number")
+        G[0][1]["edge-number"] = np.float64(1.1)
+
+        expected = f"""<gexf xmlns="http://www.gexf.net/1.2draft"\
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation\
+="http://www.gexf.net/1.2draft http://www.gexf.net/1.2draft/gexf.xsd"\
+ version="1.2">
+  <meta lastmodifieddate="{time.strftime('%Y-%m-%d')}">
+    <creator>NetworkX {nx.__version__}</creator>
+  </meta>
+  <graph defaultedgetype="undirected" mode="static" name="">
+    <attributes mode="static" class="edge">
+      <attribute id="1" title="edge-number" type="float" />
+    </attributes>
+    <attributes mode="static" class="node">
+      <attribute id="0" title="number" type="int" />
+    </attributes>
+    <nodes>
+      <node id="0" label="0">
+        <attvalues>
+          <attvalue for="0" value="0" />
+        </attvalues>
+      </node>
+      <node id="1" label="1">
+        <attvalues>
+          <attvalue for="0" value="1" />
+        </attvalues>
+      </node>
+      <node id="2" label="2">
+        <attvalues>
+          <attvalue for="0" value="2" />
+        </attvalues>
+      </node>
+      <node id="3" label="3">
+        <attvalues>
+          <attvalue for="0" value="3" />
+        </attvalues>
+      </node>
+    </nodes>
+    <edges>
+      <edge source="0" target="1" id="0">
+        <attvalues>
+          <attvalue for="1" value="1.1" />
+        </attvalues>
+      </edge>
+      <edge source="1" target="2" id="1" />
+      <edge source="2" target="3" id="2" />
+    </edges>
+  </graph>
+</gexf>"""
+        obtained = "\n".join(nx.generate_gexf(G))
+        assert expected == obtained
+
+    def test_bool(self):
+        G = nx.Graph()
+        G.add_node(1, testattr=True)
+        fh = io.BytesIO()
+        nx.write_gexf(G, fh)
+        fh.seek(0)
+        H = nx.read_gexf(fh, node_type=int)
+        assert H.nodes[1]["testattr"]
+
+    # Test for NaN, INF and -INF
+    def test_specials(self):
+        from math import isnan
+
+        inf, nan = float("inf"), float("nan")
+        G = nx.Graph()
+        G.add_node(1, testattr=inf, strdata="inf", key="a")
+        G.add_node(2, testattr=nan, strdata="nan", key="b")
+        G.add_node(3, testattr=-inf, strdata="-inf", key="c")
+
+        fh = io.BytesIO()
+        nx.write_gexf(G, fh)
+        fh.seek(0)
+        filetext = fh.read()
+        fh.seek(0)
+        H = nx.read_gexf(fh, node_type=int)
+
+        assert b"INF" in filetext
+        assert b"NaN" in filetext
+        assert b"-INF" in filetext
+
+        assert H.nodes[1]["testattr"] == inf
+        assert isnan(H.nodes[2]["testattr"])
+        assert H.nodes[3]["testattr"] == -inf
+
+        assert H.nodes[1]["strdata"] == "inf"
+        assert H.nodes[2]["strdata"] == "nan"
+        assert H.nodes[3]["strdata"] == "-inf"
+
+        assert H.nodes[1]["networkx_key"] == "a"
+        assert H.nodes[2]["networkx_key"] == "b"
+        assert H.nodes[3]["networkx_key"] == "c"
+
+    def test_simple_list(self):
+        G = nx.Graph()
+        list_value = [(1, 2, 3), (9, 1, 2)]
+        G.add_node(1, key=list_value)
+        fh = io.BytesIO()
+        nx.write_gexf(G, fh)
+        fh.seek(0)
+        H = nx.read_gexf(fh, node_type=int)
+        assert H.nodes[1]["networkx_key"] == list_value
+
+    def test_dynamic_mode(self):
+        G = nx.Graph()
+        G.add_node(1, label="1", color="green")
+        G.graph["mode"] = "dynamic"
+        fh = io.BytesIO()
+        nx.write_gexf(G, fh)
+        fh.seek(0)
+        H = nx.read_gexf(fh, node_type=int)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(sorted(e) for e in G.edges()) == sorted(
+            sorted(e) for e in H.edges()
+        )
+
+    def test_multigraph_with_missing_attributes(self):
+        G = nx.MultiGraph()
+        G.add_node(0, label="1", color="green")
+        G.add_node(1, label="2", color="green")
+        G.add_edge(0, 1, id="0", weight=3, type="undirected", start=0, end=1)
+        G.add_edge(0, 1, id="1", label="foo", start=0, end=1)
+        G.add_edge(0, 1)
+        fh = io.BytesIO()
+        nx.write_gexf(G, fh)
+        fh.seek(0)
+        H = nx.read_gexf(fh, node_type=int)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(sorted(e) for e in G.edges()) == sorted(
+            sorted(e) for e in H.edges()
+        )
+
+    def test_missing_viz_attributes(self):
+        G = nx.Graph()
+        G.add_node(0, label="1", color="green")
+        G.nodes[0]["viz"] = {"size": 54}
+        G.nodes[0]["viz"]["position"] = {"x": 0, "y": 1, "z": 0}
+        G.nodes[0]["viz"]["color"] = {"r": 0, "g": 0, "b": 256}
+        G.nodes[0]["viz"]["shape"] = "http://random.url"
+        G.nodes[0]["viz"]["thickness"] = 2
+        fh = io.BytesIO()
+        nx.write_gexf(G, fh, version="1.1draft")
+        fh.seek(0)
+        H = nx.read_gexf(fh, node_type=int)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(sorted(e) for e in G.edges()) == sorted(
+            sorted(e) for e in H.edges()
+        )
+
+        # Test missing alpha value for version >draft1.1 - set default alpha value
+        # to 1.0 instead of `None` when writing for better general compatibility
+        fh = io.BytesIO()
+        # G.nodes[0]["viz"]["color"] does not have an alpha value explicitly defined
+        # so the default is used instead
+        nx.write_gexf(G, fh, version="1.2draft")
+        fh.seek(0)
+        H = nx.read_gexf(fh, node_type=int)
+        assert H.nodes[0]["viz"]["color"]["a"] == 1.0
+
+        # Second graph for the other branch
+        G = nx.Graph()
+        G.add_node(0, label="1", color="green")
+        G.nodes[0]["viz"] = {"size": 54}
+        G.nodes[0]["viz"]["position"] = {"x": 0, "y": 1, "z": 0}
+        G.nodes[0]["viz"]["color"] = {"r": 0, "g": 0, "b": 256, "a": 0.5}
+        G.nodes[0]["viz"]["shape"] = "ftp://random.url"
+        G.nodes[0]["viz"]["thickness"] = 2
+        fh = io.BytesIO()
+        nx.write_gexf(G, fh)
+        fh.seek(0)
+        H = nx.read_gexf(fh, node_type=int)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(sorted(e) for e in G.edges()) == sorted(
+            sorted(e) for e in H.edges()
+        )
+
+    def test_slice_and_spell(self):
+        # Test spell first, so version = 1.2
+        G = nx.Graph()
+        G.add_node(0, label="1", color="green")
+        G.nodes[0]["spells"] = [(1, 2)]
+        fh = io.BytesIO()
+        nx.write_gexf(G, fh)
+        fh.seek(0)
+        H = nx.read_gexf(fh, node_type=int)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(sorted(e) for e in G.edges()) == sorted(
+            sorted(e) for e in H.edges()
+        )
+
+        G = nx.Graph()
+        G.add_node(0, label="1", color="green")
+        G.nodes[0]["slices"] = [(1, 2)]
+        fh = io.BytesIO()
+        nx.write_gexf(G, fh, version="1.1draft")
+        fh.seek(0)
+        H = nx.read_gexf(fh, node_type=int)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(sorted(e) for e in G.edges()) == sorted(
+            sorted(e) for e in H.edges()
+        )
+
+    def test_add_parent(self):
+        G = nx.Graph()
+        G.add_node(0, label="1", color="green", parents=[1, 2])
+        fh = io.BytesIO()
+        nx.write_gexf(G, fh)
+        fh.seek(0)
+        H = nx.read_gexf(fh, node_type=int)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(sorted(e) for e in G.edges()) == sorted(
+            sorted(e) for e in H.edges()
+        )
diff --git a/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_gml.py b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_gml.py
new file mode 100644
index 00000000..f575ad26
--- /dev/null
+++ b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_gml.py
@@ -0,0 +1,744 @@
+import codecs
+import io
+import math
+from ast import literal_eval
+from contextlib import contextmanager
+from textwrap import dedent
+
+import pytest
+
+import networkx as nx
+from networkx.readwrite.gml import literal_destringizer, literal_stringizer
+
+
+class TestGraph:
+    @classmethod
+    def setup_class(cls):
+        cls.simple_data = """Creator "me"
+Version "xx"
+graph [
+ comment "This is a sample graph"
+ directed 1
+ IsPlanar 1
+ pos  [ x 0 y 1 ]
+ node [
+   id 1
+   label "Node 1"
+   pos [ x 1 y 1 ]
+ ]
+ node [
+    id 2
+    pos [ x 1 y 2 ]
+    label "Node 2"
+    ]
+  node [
+    id 3
+    label "Node 3"
+    pos [ x 1 y 3 ]
+  ]
+  edge [
+    source 1
+    target 2
+    label "Edge from node 1 to node 2"
+    color [line "blue" thickness 3]
+
+  ]
+  edge [
+    source 2
+    target 3
+    label "Edge from node 2 to node 3"
+  ]
+  edge [
+    source 3
+    target 1
+    label "Edge from node 3 to node 1"
+  ]
+]
+"""
+
+    def test_parse_gml_cytoscape_bug(self):
+        # example from issue #321, originally #324 in trac
+        cytoscape_example = """
+Creator "Cytoscape"
+Version 1.0
+graph   [
+    node    [
+        root_index  -3
+        id  -3
+        graphics    [
+            x   -96.0
+            y   -67.0
+            w   40.0
+            h   40.0
+            fill    "#ff9999"
+            type    "ellipse"
+            outline "#666666"
+            outline_width   1.5
+        ]
+        label   "node2"
+    ]
+    node    [
+        root_index  -2
+        id  -2
+        graphics    [
+            x   63.0
+            y   37.0
+            w   40.0
+            h   40.0
+            fill    "#ff9999"
+            type    "ellipse"
+            outline "#666666"
+            outline_width   1.5
+        ]
+        label   "node1"
+    ]
+    node    [
+        root_index  -1
+        id  -1
+        graphics    [
+            x   -31.0
+            y   -17.0
+            w   40.0
+            h   40.0
+            fill    "#ff9999"
+            type    "ellipse"
+            outline "#666666"
+            outline_width   1.5
+        ]
+        label   "node0"
+    ]
+    edge    [
+        root_index  -2
+        target  -2
+        source  -1
+        graphics    [
+            width   1.5
+            fill    "#0000ff"
+            type    "line"
+            Line    [
+            ]
+            source_arrow    0
+            target_arrow    3
+        ]
+        label   "DirectedEdge"
+    ]
+    edge    [
+        root_index  -1
+        target  -1
+        source  -3
+        graphics    [
+            width   1.5
+            fill    "#0000ff"
+            type    "line"
+            Line    [
+            ]
+            source_arrow    0
+            target_arrow    3
+        ]
+        label   "DirectedEdge"
+    ]
+]
+"""
+        nx.parse_gml(cytoscape_example)
+
+    def test_parse_gml(self):
+        G = nx.parse_gml(self.simple_data, label="label")
+        assert sorted(G.nodes()) == ["Node 1", "Node 2", "Node 3"]
+        assert sorted(G.edges()) == [
+            ("Node 1", "Node 2"),
+            ("Node 2", "Node 3"),
+            ("Node 3", "Node 1"),
+        ]
+
+        assert sorted(G.edges(data=True)) == [
+            (
+                "Node 1",
+                "Node 2",
+                {
+                    "color": {"line": "blue", "thickness": 3},
+                    "label": "Edge from node 1 to node 2",
+                },
+            ),
+            ("Node 2", "Node 3", {"label": "Edge from node 2 to node 3"}),
+            ("Node 3", "Node 1", {"label": "Edge from node 3 to node 1"}),
+        ]
+
+    def test_read_gml(self, tmp_path):
+        fname = tmp_path / "test.gml"
+        with open(fname, "w") as fh:
+            fh.write(self.simple_data)
+        Gin = nx.read_gml(fname, label="label")
+        G = nx.parse_gml(self.simple_data, label="label")
+        assert sorted(G.nodes(data=True)) == sorted(Gin.nodes(data=True))
+        assert sorted(G.edges(data=True)) == sorted(Gin.edges(data=True))
+
+    def test_labels_are_strings(self):
+        # GML requires labels to be strings (i.e., in quotes)
+        answer = """graph [
+  node [
+    id 0
+    label "1203"
+  ]
+]"""
+        G = nx.Graph()
+        G.add_node(1203)
+        data = "\n".join(nx.generate_gml(G, stringizer=literal_stringizer))
+        assert data == answer
+
+    def test_relabel_duplicate(self):
+        data = """
+graph
+[
+        label   ""
+        directed        1
+        node
+        [
+                id      0
+                label   "same"
+        ]
+        node
+        [
+                id      1
+                label   "same"
+        ]
+]
+"""
+        fh = io.BytesIO(data.encode("UTF-8"))
+        fh.seek(0)
+        pytest.raises(nx.NetworkXError, nx.read_gml, fh, label="label")
+
+    @pytest.mark.parametrize("stringizer", (None, literal_stringizer))
+    def test_tuplelabels(self, stringizer):
+        # https://github.com/networkx/networkx/pull/1048
+        # Writing tuple labels to GML failed.
+        G = nx.Graph()
+        G.add_edge((0, 1), (1, 0))
+        data = "\n".join(nx.generate_gml(G, stringizer=stringizer))
+        answer = """graph [
+  node [
+    id 0
+    label "(0,1)"
+  ]
+  node [
+    id 1
+    label "(1,0)"
+  ]
+  edge [
+    source 0
+    target 1
+  ]
+]"""
+        assert data == answer
+
+    def test_quotes(self, tmp_path):
+        # https://github.com/networkx/networkx/issues/1061
+        # Encoding quotes as HTML entities.
+        G = nx.path_graph(1)
+        G.name = "path_graph(1)"
+        attr = 'This is "quoted" and this is a copyright: ' + chr(169)
+        G.nodes[0]["demo"] = attr
+        with open(tmp_path / "test.gml", "w+b") as fobj:
+            nx.write_gml(G, fobj)
+            fobj.seek(0)
+            # Should be bytes in 2.x and 3.x
+            data = fobj.read().strip().decode("ascii")
+        answer = """graph [
+  name "path_graph(1)"
+  node [
+    id 0
+    label "0"
+    demo "This is &#34;quoted&#34; and this is a copyright: &#169;"
+  ]
+]"""
+        assert data == answer
+
+    def test_unicode_node(self, tmp_path):
+        node = "node" + chr(169)
+        G = nx.Graph()
+        G.add_node(node)
+        with open(tmp_path / "test.gml", "w+b") as fobj:
+            nx.write_gml(G, fobj)
+            fobj.seek(0)
+            # Should be bytes in 2.x and 3.x
+            data = fobj.read().strip().decode("ascii")
+        answer = """graph [
+  node [
+    id 0
+    label "node&#169;"
+  ]
+]"""
+        assert data == answer
+
+    def test_float_label(self, tmp_path):
+        node = 1.0
+        G = nx.Graph()
+        G.add_node(node)
+        with open(tmp_path / "test.gml", "w+b") as fobj:
+            nx.write_gml(G, fobj)
+            fobj.seek(0)
+            # Should be bytes in 2.x and 3.x
+            data = fobj.read().strip().decode("ascii")
+        answer = """graph [
+  node [
+    id 0
+    label "1.0"
+  ]
+]"""
+        assert data == answer
+
+    def test_special_float_label(self, tmp_path):
+        special_floats = [float("nan"), float("+inf"), float("-inf")]
+        try:
+            import numpy as np
+
+            special_floats += [np.nan, np.inf, np.inf * -1]
+        except ImportError:
+            special_floats += special_floats
+
+        G = nx.cycle_graph(len(special_floats))
+        attrs = dict(enumerate(special_floats))
+        nx.set_node_attributes(G, attrs, "nodefloat")
+        edges = list(G.edges)
+        attrs = {edges[i]: value for i, value in enumerate(special_floats)}
+        nx.set_edge_attributes(G, attrs, "edgefloat")
+
+        with open(tmp_path / "test.gml", "w+b") as fobj:
+            nx.write_gml(G, fobj)
+            fobj.seek(0)
+            # Should be bytes in 2.x and 3.x
+            data = fobj.read().strip().decode("ascii")
+            answer = """graph [
+  node [
+    id 0
+    label "0"
+    nodefloat NAN
+  ]
+  node [
+    id 1
+    label "1"
+    nodefloat +INF
+  ]
+  node [
+    id 2
+    label "2"
+    nodefloat -INF
+  ]
+  node [
+    id 3
+    label "3"
+    nodefloat NAN
+  ]
+  node [
+    id 4
+    label "4"
+    nodefloat +INF
+  ]
+  node [
+    id 5
+    label "5"
+    nodefloat -INF
+  ]
+  edge [
+    source 0
+    target 1
+    edgefloat NAN
+  ]
+  edge [
+    source 0
+    target 5
+    edgefloat +INF
+  ]
+  edge [
+    source 1
+    target 2
+    edgefloat -INF
+  ]
+  edge [
+    source 2
+    target 3
+    edgefloat NAN
+  ]
+  edge [
+    source 3
+    target 4
+    edgefloat +INF
+  ]
+  edge [
+    source 4
+    target 5
+    edgefloat -INF
+  ]
+]"""
+            assert data == answer
+
+            fobj.seek(0)
+            graph = nx.read_gml(fobj)
+            for indx, value in enumerate(special_floats):
+                node_value = graph.nodes[str(indx)]["nodefloat"]
+                if math.isnan(value):
+                    assert math.isnan(node_value)
+                else:
+                    assert node_value == value
+
+                edge = edges[indx]
+                string_edge = (str(edge[0]), str(edge[1]))
+                edge_value = graph.edges[string_edge]["edgefloat"]
+                if math.isnan(value):
+                    assert math.isnan(edge_value)
+                else:
+                    assert edge_value == value
+
+    def test_name(self):
+        G = nx.parse_gml('graph [ name "x" node [ id 0 label "x" ] ]')
+        assert "x" == G.graph["name"]
+        G = nx.parse_gml('graph [ node [ id 0 label "x" ] ]')
+        assert "" == G.name
+        assert "name" not in G.graph
+
+    def test_graph_types(self):
+        for directed in [None, False, True]:
+            for multigraph in [None, False, True]:
+                gml = "graph ["
+                if directed is not None:
+                    gml += " directed " + str(int(directed))
+                if multigraph is not None:
+                    gml += " multigraph " + str(int(multigraph))
+                gml += ' node [ id 0 label "0" ]'
+                gml += " edge [ source 0 target 0 ]"
+                gml += " ]"
+                G = nx.parse_gml(gml)
+                assert bool(directed) == G.is_directed()
+                assert bool(multigraph) == G.is_multigraph()
+                gml = "graph [\n"
+                if directed is True:
+                    gml += "  directed 1\n"
+                if multigraph is True:
+                    gml += "  multigraph 1\n"
+                gml += """  node [
+    id 0
+    label "0"
+  ]
+  edge [
+    source 0
+    target 0
+"""
+                if multigraph:
+                    gml += "    key 0\n"
+                gml += "  ]\n]"
+                assert gml == "\n".join(nx.generate_gml(G))
+
+    def test_data_types(self):
+        data = [
+            True,
+            False,
+            10**20,
+            -2e33,
+            "'",
+            '"&&amp;&&#34;"',
+            [{(b"\xfd",): "\x7f", chr(0x4444): (1, 2)}, (2, "3")],
+        ]
+        data.append(chr(0x14444))
+        data.append(literal_eval("{2.3j, 1 - 2.3j, ()}"))
+        G = nx.Graph()
+        G.name = data
+        G.graph["data"] = data
+        G.add_node(0, int=-1, data={"data": data})
+        G.add_edge(0, 0, float=-2.5, data=data)
+        gml = "\n".join(nx.generate_gml(G, stringizer=literal_stringizer))
+        G = nx.parse_gml(gml, destringizer=literal_destringizer)
+        assert data == G.name
+        assert {"name": data, "data": data} == G.graph
+        assert list(G.nodes(data=True)) == [(0, {"int": -1, "data": {"data": data}})]
+        assert list(G.edges(data=True)) == [(0, 0, {"float": -2.5, "data": data})]
+        G = nx.Graph()
+        G.graph["data"] = "frozenset([1, 2, 3])"
+        G = nx.parse_gml(nx.generate_gml(G), destringizer=literal_eval)
+        assert G.graph["data"] == "frozenset([1, 2, 3])"
+
+    def test_escape_unescape(self):
+        gml = """graph [
+  name "&amp;&#34;&#xf;&#x4444;&#1234567890;&#x1234567890abcdef;&unknown;"
+]"""
+        G = nx.parse_gml(gml)
+        assert (
+            '&"\x0f' + chr(0x4444) + "&#1234567890;&#x1234567890abcdef;&unknown;"
+            == G.name
+        )
+        gml = "\n".join(nx.generate_gml(G))
+        alnu = "#1234567890;&#38;#x1234567890abcdef"
+        answer = (
+            """graph [
+  name "&#38;&#34;&#15;&#17476;&#38;"""
+            + alnu
+            + """;&#38;unknown;"
+]"""
+        )
+        assert answer == gml
+
+    def test_exceptions(self, tmp_path):
+        pytest.raises(ValueError, literal_destringizer, "(")
+        pytest.raises(ValueError, literal_destringizer, "frozenset([1, 2, 3])")
+        pytest.raises(ValueError, literal_destringizer, literal_destringizer)
+        pytest.raises(ValueError, literal_stringizer, frozenset([1, 2, 3]))
+        pytest.raises(ValueError, literal_stringizer, literal_stringizer)
+        with open(tmp_path / "test.gml", "w+b") as f:
+            f.write(codecs.BOM_UTF8 + b"graph[]")
+            f.seek(0)
+            pytest.raises(nx.NetworkXError, nx.read_gml, f)
+
+        def assert_parse_error(gml):
+            pytest.raises(nx.NetworkXError, nx.parse_gml, gml)
+
+        assert_parse_error(["graph [\n\n", "]"])
+        assert_parse_error("")
+        assert_parse_error('Creator ""')
+        assert_parse_error("0")
+        assert_parse_error("graph ]")
+        assert_parse_error("graph [ 1 ]")
+        assert_parse_error("graph [ 1.E+2 ]")
+        assert_parse_error('graph [ "A" ]')
+        assert_parse_error("graph [ ] graph ]")
+        assert_parse_error("graph [ ] graph [ ]")
+        assert_parse_error("graph [ data [1, 2, 3] ]")
+        assert_parse_error("graph [ node [ ] ]")
+        assert_parse_error("graph [ node [ id 0 ] ]")
+        nx.parse_gml('graph [ node [ id "a" ] ]', label="id")
+        assert_parse_error("graph [ node [ id 0 label 0 ] node [ id 0 label 1 ] ]")
+        assert_parse_error("graph [ node [ id 0 label 0 ] node [ id 1 label 0 ] ]")
+        assert_parse_error("graph [ node [ id 0 label 0 ] edge [ ] ]")
+        assert_parse_error("graph [ node [ id 0 label 0 ] edge [ source 0 ] ]")
+        nx.parse_gml("graph [edge [ source 0 target 0 ] node [ id 0 label 0 ] ]")
+        assert_parse_error("graph [ node [ id 0 label 0 ] edge [ source 1 target 0 ] ]")
+        assert_parse_error("graph [ node [ id 0 label 0 ] edge [ source 0 target 1 ] ]")
+        assert_parse_error(
+            "graph [ node [ id 0 label 0 ] node [ id 1 label 1 ] "
+            "edge [ source 0 target 1 ] edge [ source 1 target 0 ] ]"
+        )
+        nx.parse_gml(
+            "graph [ node [ id 0 label 0 ] node [ id 1 label 1 ] "
+            "edge [ source 0 target 1 ] edge [ source 1 target 0 ] "
+            "directed 1 ]"
+        )
+        nx.parse_gml(
+            "graph [ node [ id 0 label 0 ] node [ id 1 label 1 ] "
+            "edge [ source 0 target 1 ] edge [ source 0 target 1 ]"
+            "multigraph 1 ]"
+        )
+        nx.parse_gml(
+            "graph [ node [ id 0 label 0 ] node [ id 1 label 1 ] "
+            "edge [ source 0 target 1 key 0 ] edge [ source 0 target 1 ]"
+            "multigraph 1 ]"
+        )
+        assert_parse_error(
+            "graph [ node [ id 0 label 0 ] node [ id 1 label 1 ] "
+            "edge [ source 0 target 1 key 0 ] edge [ source 0 target 1 key 0 ]"
+            "multigraph 1 ]"
+        )
+        nx.parse_gml(
+            "graph [ node [ id 0 label 0 ] node [ id 1 label 1 ] "
+            "edge [ source 0 target 1 key 0 ] edge [ source 1 target 0 key 0 ]"
+            "directed 1 multigraph 1 ]"
+        )
+
+        # Tests for string convertible alphanumeric id and label values
+        nx.parse_gml("graph [edge [ source a target a ] node [ id a label b ] ]")
+        nx.parse_gml(
+            "graph [ node [ id n42 label 0 ] node [ id x43 label 1 ]"
+            "edge [ source n42 target x43 key 0 ]"
+            "edge [ source x43 target n42 key 0 ]"
+            "directed 1 multigraph 1 ]"
+        )
+        assert_parse_error(
+            "graph [edge [ source '\u4200' target '\u4200' ] "
+            + "node [ id '\u4200' label b ] ]"
+        )
+
+        def assert_generate_error(*args, **kwargs):
+            pytest.raises(
+                nx.NetworkXError, lambda: list(nx.generate_gml(*args, **kwargs))
+            )
+
+        G = nx.Graph()
+        G.graph[3] = 3
+        assert_generate_error(G)
+        G = nx.Graph()
+        G.graph["3"] = 3
+        assert_generate_error(G)
+        G = nx.Graph()
+        G.graph["data"] = frozenset([1, 2, 3])
+        assert_generate_error(G, stringizer=literal_stringizer)
+
+    def test_label_kwarg(self):
+        G = nx.parse_gml(self.simple_data, label="id")
+        assert sorted(G.nodes) == [1, 2, 3]
+        labels = [G.nodes[n]["label"] for n in sorted(G.nodes)]
+        assert labels == ["Node 1", "Node 2", "Node 3"]
+
+        G = nx.parse_gml(self.simple_data, label=None)
+        assert sorted(G.nodes) == [1, 2, 3]
+        labels = [G.nodes[n]["label"] for n in sorted(G.nodes)]
+        assert labels == ["Node 1", "Node 2", "Node 3"]
+
+    def test_outofrange_integers(self, tmp_path):
+        # GML restricts integers to 32 signed bits.
+        # Check that we honor this restriction on export
+        G = nx.Graph()
+        # Test export for numbers that barely fit or don't fit into 32 bits,
+        # and 3 numbers in the middle
+        numbers = {
+            "toosmall": (-(2**31)) - 1,
+            "small": -(2**31),
+            "med1": -4,
+            "med2": 0,
+            "med3": 17,
+            "big": (2**31) - 1,
+            "toobig": 2**31,
+        }
+        G.add_node("Node", **numbers)
+
+        fname = tmp_path / "test.gml"
+        nx.write_gml(G, fname)
+        # Check that the export wrote the nonfitting numbers as strings
+        G2 = nx.read_gml(fname)
+        for attr, value in G2.nodes["Node"].items():
+            if attr == "toosmall" or attr == "toobig":
+                assert type(value) == str
+            else:
+                assert type(value) == int
+
+    def test_multiline(self):
+        # example from issue #6836
+        multiline_example = """
+graph
+[
+    node
+    [
+	    id 0
+	    label "multiline node"
+	    label2 "multiline1
+    multiline2
+    multiline3"
+	    alt_name "id 0"
+    ]
+]
+"""
+        G = nx.parse_gml(multiline_example)
+        assert G.nodes["multiline node"] == {
+            "label2": "multiline1 multiline2 multiline3",
+            "alt_name": "id 0",
+        }
+
+
+@contextmanager
+def byte_file():
+    _file_handle = io.BytesIO()
+    yield _file_handle
+    _file_handle.seek(0)
+
+
+class TestPropertyLists:
+    def test_writing_graph_with_multi_element_property_list(self):
+        g = nx.Graph()
+        g.add_node("n1", properties=["element", 0, 1, 2.5, True, False])
+        with byte_file() as f:
+            nx.write_gml(g, f)
+        result = f.read().decode()
+
+        assert result == dedent(
+            """\
+            graph [
+              node [
+                id 0
+                label "n1"
+                properties "element"
+                properties 0
+                properties 1
+                properties 2.5
+                properties 1
+                properties 0
+              ]
+            ]
+        """
+        )
+
+    def test_writing_graph_with_one_element_property_list(self):
+        g = nx.Graph()
+        g.add_node("n1", properties=["element"])
+        with byte_file() as f:
+            nx.write_gml(g, f)
+        result = f.read().decode()
+
+        assert result == dedent(
+            """\
+            graph [
+              node [
+                id 0
+                label "n1"
+                properties "_networkx_list_start"
+                properties "element"
+              ]
+            ]
+        """
+        )
+
+    def test_reading_graph_with_list_property(self):
+        with byte_file() as f:
+            f.write(
+                dedent(
+                    """
+              graph [
+                node [
+                  id 0
+                  label "n1"
+                  properties "element"
+                  properties 0
+                  properties 1
+                  properties 2.5
+                ]
+              ]
+            """
+                ).encode("ascii")
+            )
+            f.seek(0)
+            graph = nx.read_gml(f)
+        assert graph.nodes(data=True)["n1"] == {"properties": ["element", 0, 1, 2.5]}
+
+    def test_reading_graph_with_single_element_list_property(self):
+        with byte_file() as f:
+            f.write(
+                dedent(
+                    """
+              graph [
+                node [
+                  id 0
+                  label "n1"
+                  properties "_networkx_list_start"
+                  properties "element"
+                ]
+              ]
+            """
+                ).encode("ascii")
+            )
+            f.seek(0)
+            graph = nx.read_gml(f)
+        assert graph.nodes(data=True)["n1"] == {"properties": ["element"]}
+
+
+@pytest.mark.parametrize("coll", ([], ()))
+def test_stringize_empty_list_tuple(coll):
+    G = nx.path_graph(2)
+    G.nodes[0]["test"] = coll  # test serializing an empty collection
+    f = io.BytesIO()
+    nx.write_gml(G, f)  # Smoke test - should not raise
+    f.seek(0)
+    H = nx.read_gml(f)
+    assert H.nodes["0"]["test"] == coll  # Check empty list round-trips properly
+    # Check full round-tripping. Note that nodes are loaded as strings by
+    # default, so there needs to be some remapping prior to comparison
+    H = nx.relabel_nodes(H, {"0": 0, "1": 1})
+    assert nx.utils.graphs_equal(G, H)
+    # Same as above, but use destringizer for node remapping. Should have no
+    # effect on node attr
+    f.seek(0)
+    H = nx.read_gml(f, destringizer=int)
+    assert nx.utils.graphs_equal(G, H)
diff --git a/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_graph6.py b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_graph6.py
new file mode 100644
index 00000000..a8032694
--- /dev/null
+++ b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_graph6.py
@@ -0,0 +1,168 @@
+from io import BytesIO
+
+import pytest
+
+import networkx as nx
+import networkx.readwrite.graph6 as g6
+from networkx.utils import edges_equal, nodes_equal
+
+
+class TestGraph6Utils:
+    def test_n_data_n_conversion(self):
+        for i in [0, 1, 42, 62, 63, 64, 258047, 258048, 7744773, 68719476735]:
+            assert g6.data_to_n(g6.n_to_data(i))[0] == i
+            assert g6.data_to_n(g6.n_to_data(i))[1] == []
+            assert g6.data_to_n(g6.n_to_data(i) + [42, 43])[1] == [42, 43]
+
+
+class TestFromGraph6Bytes:
+    def test_from_graph6_bytes(self):
+        data = b"DF{"
+        G = nx.from_graph6_bytes(data)
+        assert nodes_equal(G.nodes(), [0, 1, 2, 3, 4])
+        assert edges_equal(
+            G.edges(), [(0, 3), (0, 4), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]
+        )
+
+    def test_read_equals_from_bytes(self):
+        data = b"DF{"
+        G = nx.from_graph6_bytes(data)
+        fh = BytesIO(data)
+        Gin = nx.read_graph6(fh)
+        assert nodes_equal(G.nodes(), Gin.nodes())
+        assert edges_equal(G.edges(), Gin.edges())
+
+
+class TestReadGraph6:
+    def test_read_many_graph6(self):
+        """Test for reading many graphs from a file into a list."""
+        data = b"DF{\nD`{\nDqK\nD~{\n"
+        fh = BytesIO(data)
+        glist = nx.read_graph6(fh)
+        assert len(glist) == 4
+        for G in glist:
+            assert sorted(G) == list(range(5))
+
+
+class TestWriteGraph6:
+    """Unit tests for writing a graph to a file in graph6 format."""
+
+    def test_null_graph(self):
+        result = BytesIO()
+        nx.write_graph6(nx.null_graph(), result)
+        assert result.getvalue() == b">>graph6<<?\n"
+
+    def test_trivial_graph(self):
+        result = BytesIO()
+        nx.write_graph6(nx.trivial_graph(), result)
+        assert result.getvalue() == b">>graph6<<@\n"
+
+    def test_complete_graph(self):
+        result = BytesIO()
+        nx.write_graph6(nx.complete_graph(4), result)
+        assert result.getvalue() == b">>graph6<<C~\n"
+
+    def test_large_complete_graph(self):
+        result = BytesIO()
+        nx.write_graph6(nx.complete_graph(67), result, header=False)
+        assert result.getvalue() == b"~?@B" + b"~" * 368 + b"w\n"
+
+    def test_no_header(self):
+        result = BytesIO()
+        nx.write_graph6(nx.complete_graph(4), result, header=False)
+        assert result.getvalue() == b"C~\n"
+
+    def test_complete_bipartite_graph(self):
+        result = BytesIO()
+        G = nx.complete_bipartite_graph(6, 9)
+        nx.write_graph6(G, result, header=False)
+        # The expected encoding here was verified by Sage.
+        assert result.getvalue() == b"N??F~z{~Fw^_~?~?^_?\n"
+
+    @pytest.mark.parametrize("G", (nx.MultiGraph(), nx.DiGraph()))
+    def test_no_directed_or_multi_graphs(self, G):
+        with pytest.raises(nx.NetworkXNotImplemented):
+            nx.write_graph6(G, BytesIO())
+
+    def test_length(self):
+        for i in list(range(13)) + [31, 47, 62, 63, 64, 72]:
+            g = nx.random_graphs.gnm_random_graph(i, i * i // 4, seed=i)
+            gstr = BytesIO()
+            nx.write_graph6(g, gstr, header=False)
+            # Strip the trailing newline.
+            gstr = gstr.getvalue().rstrip()
+            assert len(gstr) == ((i - 1) * i // 2 + 5) // 6 + (1 if i < 63 else 4)
+
+    def test_roundtrip(self):
+        for i in list(range(13)) + [31, 47, 62, 63, 64, 72]:
+            G = nx.random_graphs.gnm_random_graph(i, i * i // 4, seed=i)
+            f = BytesIO()
+            nx.write_graph6(G, f)
+            f.seek(0)
+            H = nx.read_graph6(f)
+            assert nodes_equal(G.nodes(), H.nodes())
+            assert edges_equal(G.edges(), H.edges())
+
+    def test_write_path(self, tmp_path):
+        with open(tmp_path / "test.g6", "w+b") as f:
+            g6.write_graph6_file(nx.null_graph(), f)
+            f.seek(0)
+            assert f.read() == b">>graph6<<?\n"
+
+    @pytest.mark.parametrize("edge", ((0, 1), (1, 2), (1, 42)))
+    def test_relabeling(self, edge):
+        G = nx.Graph([edge])
+        f = BytesIO()
+        nx.write_graph6(G, f)
+        f.seek(0)
+        assert f.read() == b">>graph6<<A_\n"
+
+
+class TestToGraph6Bytes:
+    def test_null_graph(self):
+        G = nx.null_graph()
+        assert g6.to_graph6_bytes(G) == b">>graph6<<?\n"
+
+    def test_trivial_graph(self):
+        G = nx.trivial_graph()
+        assert g6.to_graph6_bytes(G) == b">>graph6<<@\n"
+
+    def test_complete_graph(self):
+        assert g6.to_graph6_bytes(nx.complete_graph(4)) == b">>graph6<<C~\n"
+
+    def test_large_complete_graph(self):
+        G = nx.complete_graph(67)
+        assert g6.to_graph6_bytes(G, header=False) == b"~?@B" + b"~" * 368 + b"w\n"
+
+    def test_no_header(self):
+        G = nx.complete_graph(4)
+        assert g6.to_graph6_bytes(G, header=False) == b"C~\n"
+
+    def test_complete_bipartite_graph(self):
+        G = nx.complete_bipartite_graph(6, 9)
+        assert g6.to_graph6_bytes(G, header=False) == b"N??F~z{~Fw^_~?~?^_?\n"
+
+    @pytest.mark.parametrize("G", (nx.MultiGraph(), nx.DiGraph()))
+    def test_no_directed_or_multi_graphs(self, G):
+        with pytest.raises(nx.NetworkXNotImplemented):
+            g6.to_graph6_bytes(G)
+
+    def test_length(self):
+        for i in list(range(13)) + [31, 47, 62, 63, 64, 72]:
+            G = nx.random_graphs.gnm_random_graph(i, i * i // 4, seed=i)
+            # Strip the trailing newline.
+            gstr = g6.to_graph6_bytes(G, header=False).rstrip()
+            assert len(gstr) == ((i - 1) * i // 2 + 5) // 6 + (1 if i < 63 else 4)
+
+    def test_roundtrip(self):
+        for i in list(range(13)) + [31, 47, 62, 63, 64, 72]:
+            G = nx.random_graphs.gnm_random_graph(i, i * i // 4, seed=i)
+            data = g6.to_graph6_bytes(G)
+            H = nx.from_graph6_bytes(data.rstrip())
+            assert nodes_equal(G.nodes(), H.nodes())
+            assert edges_equal(G.edges(), H.edges())
+
+    @pytest.mark.parametrize("edge", ((0, 1), (1, 2), (1, 42)))
+    def test_relabeling(self, edge):
+        G = nx.Graph([edge])
+        assert g6.to_graph6_bytes(G) == b">>graph6<<A_\n"
diff --git a/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_graphml.py b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_graphml.py
new file mode 100644
index 00000000..5ffa837e
--- /dev/null
+++ b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_graphml.py
@@ -0,0 +1,1531 @@
+import io
+
+import pytest
+
+import networkx as nx
+from networkx.readwrite.graphml import GraphMLWriter
+from networkx.utils import edges_equal, nodes_equal
+
+
+class BaseGraphML:
+    @classmethod
+    def setup_class(cls):
+        cls.simple_directed_data = """<?xml version="1.0" encoding="UTF-8"?>
+<!-- This file was written by the JAVA GraphML Library.-->
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <graph id="G" edgedefault="directed">
+    <node id="n0"/>
+    <node id="n1"/>
+    <node id="n2"/>
+    <node id="n3"/>
+    <node id="n4"/>
+    <node id="n5"/>
+    <node id="n6"/>
+    <node id="n7"/>
+    <node id="n8"/>
+    <node id="n9"/>
+    <node id="n10"/>
+    <edge id="foo" source="n0" target="n2"/>
+    <edge source="n1" target="n2"/>
+    <edge source="n2" target="n3"/>
+    <edge source="n3" target="n5"/>
+    <edge source="n3" target="n4"/>
+    <edge source="n4" target="n6"/>
+    <edge source="n6" target="n5"/>
+    <edge source="n5" target="n7"/>
+    <edge source="n6" target="n8"/>
+    <edge source="n8" target="n7"/>
+    <edge source="n8" target="n9"/>
+  </graph>
+</graphml>"""
+        cls.simple_directed_graph = nx.DiGraph()
+        cls.simple_directed_graph.add_node("n10")
+        cls.simple_directed_graph.add_edge("n0", "n2", id="foo")
+        cls.simple_directed_graph.add_edge("n0", "n2")
+        cls.simple_directed_graph.add_edges_from(
+            [
+                ("n1", "n2"),
+                ("n2", "n3"),
+                ("n3", "n5"),
+                ("n3", "n4"),
+                ("n4", "n6"),
+                ("n6", "n5"),
+                ("n5", "n7"),
+                ("n6", "n8"),
+                ("n8", "n7"),
+                ("n8", "n9"),
+            ]
+        )
+        cls.simple_directed_fh = io.BytesIO(cls.simple_directed_data.encode("UTF-8"))
+
+        cls.attribute_data = """<?xml version="1.0" encoding="UTF-8"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+      xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+        http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <key id="d0" for="node" attr.name="color" attr.type="string">
+    <default>yellow</default>
+  </key>
+  <key id="d1" for="edge" attr.name="weight" attr.type="double"/>
+  <graph id="G" edgedefault="directed">
+    <node id="n0">
+      <data key="d0">green</data>
+    </node>
+    <node id="n1"/>
+    <node id="n2">
+      <data key="d0">blue</data>
+    </node>
+    <node id="n3">
+      <data key="d0">red</data>
+    </node>
+    <node id="n4"/>
+    <node id="n5">
+      <data key="d0">turquoise</data>
+    </node>
+    <edge id="e0" source="n0" target="n2">
+      <data key="d1">1.0</data>
+    </edge>
+    <edge id="e1" source="n0" target="n1">
+      <data key="d1">1.0</data>
+    </edge>
+    <edge id="e2" source="n1" target="n3">
+      <data key="d1">2.0</data>
+    </edge>
+    <edge id="e3" source="n3" target="n2"/>
+    <edge id="e4" source="n2" target="n4"/>
+    <edge id="e5" source="n3" target="n5"/>
+    <edge id="e6" source="n5" target="n4">
+      <data key="d1">1.1</data>
+    </edge>
+  </graph>
+</graphml>
+"""
+        cls.attribute_graph = nx.DiGraph(id="G")
+        cls.attribute_graph.graph["node_default"] = {"color": "yellow"}
+        cls.attribute_graph.add_node("n0", color="green")
+        cls.attribute_graph.add_node("n2", color="blue")
+        cls.attribute_graph.add_node("n3", color="red")
+        cls.attribute_graph.add_node("n4")
+        cls.attribute_graph.add_node("n5", color="turquoise")
+        cls.attribute_graph.add_edge("n0", "n2", id="e0", weight=1.0)
+        cls.attribute_graph.add_edge("n0", "n1", id="e1", weight=1.0)
+        cls.attribute_graph.add_edge("n1", "n3", id="e2", weight=2.0)
+        cls.attribute_graph.add_edge("n3", "n2", id="e3")
+        cls.attribute_graph.add_edge("n2", "n4", id="e4")
+        cls.attribute_graph.add_edge("n3", "n5", id="e5")
+        cls.attribute_graph.add_edge("n5", "n4", id="e6", weight=1.1)
+        cls.attribute_fh = io.BytesIO(cls.attribute_data.encode("UTF-8"))
+
+        cls.node_attribute_default_data = """<?xml version="1.0" encoding="UTF-8"?>
+        <graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+              xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+                http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+          <key id="d0" for="node" attr.name="boolean_attribute" attr.type="boolean"><default>false</default></key>
+          <key id="d1" for="node" attr.name="int_attribute" attr.type="int"><default>0</default></key>
+          <key id="d2" for="node" attr.name="long_attribute" attr.type="long"><default>0</default></key>
+          <key id="d3" for="node" attr.name="float_attribute" attr.type="float"><default>0.0</default></key>
+          <key id="d4" for="node" attr.name="double_attribute" attr.type="double"><default>0.0</default></key>
+          <key id="d5" for="node" attr.name="string_attribute" attr.type="string"><default>Foo</default></key>
+          <graph id="G" edgedefault="directed">
+            <node id="n0"/>
+            <node id="n1"/>
+            <edge id="e0" source="n0" target="n1"/>
+          </graph>
+        </graphml>
+        """
+        cls.node_attribute_default_graph = nx.DiGraph(id="G")
+        cls.node_attribute_default_graph.graph["node_default"] = {
+            "boolean_attribute": False,
+            "int_attribute": 0,
+            "long_attribute": 0,
+            "float_attribute": 0.0,
+            "double_attribute": 0.0,
+            "string_attribute": "Foo",
+        }
+        cls.node_attribute_default_graph.add_node("n0")
+        cls.node_attribute_default_graph.add_node("n1")
+        cls.node_attribute_default_graph.add_edge("n0", "n1", id="e0")
+        cls.node_attribute_default_fh = io.BytesIO(
+            cls.node_attribute_default_data.encode("UTF-8")
+        )
+
+        cls.attribute_named_key_ids_data = """<?xml version='1.0' encoding='utf-8'?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <key id="edge_prop" for="edge" attr.name="edge_prop" attr.type="string"/>
+  <key id="prop2" for="node" attr.name="prop2" attr.type="string"/>
+  <key id="prop1" for="node" attr.name="prop1" attr.type="string"/>
+  <graph edgedefault="directed">
+    <node id="0">
+      <data key="prop1">val1</data>
+      <data key="prop2">val2</data>
+    </node>
+    <node id="1">
+      <data key="prop1">val_one</data>
+      <data key="prop2">val2</data>
+    </node>
+    <edge source="0" target="1">
+      <data key="edge_prop">edge_value</data>
+    </edge>
+  </graph>
+</graphml>
+"""
+        cls.attribute_named_key_ids_graph = nx.DiGraph()
+        cls.attribute_named_key_ids_graph.add_node("0", prop1="val1", prop2="val2")
+        cls.attribute_named_key_ids_graph.add_node("1", prop1="val_one", prop2="val2")
+        cls.attribute_named_key_ids_graph.add_edge("0", "1", edge_prop="edge_value")
+        fh = io.BytesIO(cls.attribute_named_key_ids_data.encode("UTF-8"))
+        cls.attribute_named_key_ids_fh = fh
+
+        cls.attribute_numeric_type_data = """<?xml version='1.0' encoding='utf-8'?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <key attr.name="weight" attr.type="double" for="node" id="d1" />
+  <key attr.name="weight" attr.type="double" for="edge" id="d0" />
+  <graph edgedefault="directed">
+    <node id="n0">
+      <data key="d1">1</data>
+    </node>
+    <node id="n1">
+      <data key="d1">2.0</data>
+    </node>
+    <edge source="n0" target="n1">
+      <data key="d0">1</data>
+    </edge>
+    <edge source="n1" target="n0">
+      <data key="d0">k</data>
+    </edge>
+    <edge source="n1" target="n1">
+      <data key="d0">1.0</data>
+    </edge>
+  </graph>
+</graphml>
+"""
+        cls.attribute_numeric_type_graph = nx.DiGraph()
+        cls.attribute_numeric_type_graph.add_node("n0", weight=1)
+        cls.attribute_numeric_type_graph.add_node("n1", weight=2.0)
+        cls.attribute_numeric_type_graph.add_edge("n0", "n1", weight=1)
+        cls.attribute_numeric_type_graph.add_edge("n1", "n1", weight=1.0)
+        fh = io.BytesIO(cls.attribute_numeric_type_data.encode("UTF-8"))
+        cls.attribute_numeric_type_fh = fh
+
+        cls.simple_undirected_data = """<?xml version="1.0" encoding="UTF-8"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <graph id="G">
+    <node id="n0"/>
+    <node id="n1"/>
+    <node id="n2"/>
+    <node id="n10"/>
+    <edge id="foo" source="n0" target="n2"/>
+    <edge source="n1" target="n2"/>
+    <edge source="n2" target="n3"/>
+  </graph>
+</graphml>"""
+        #    <edge source="n8" target="n10" directed="false"/>
+        cls.simple_undirected_graph = nx.Graph()
+        cls.simple_undirected_graph.add_node("n10")
+        cls.simple_undirected_graph.add_edge("n0", "n2", id="foo")
+        cls.simple_undirected_graph.add_edges_from([("n1", "n2"), ("n2", "n3")])
+        fh = io.BytesIO(cls.simple_undirected_data.encode("UTF-8"))
+        cls.simple_undirected_fh = fh
+
+        cls.undirected_multigraph_data = """<?xml version="1.0" encoding="UTF-8"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <graph id="G">
+    <node id="n0"/>
+    <node id="n1"/>
+    <node id="n2"/>
+    <node id="n10"/>
+    <edge id="e0" source="n0" target="n2"/>
+    <edge id="e1" source="n1" target="n2"/>
+    <edge id="e2" source="n2" target="n1"/>
+  </graph>
+</graphml>"""
+        cls.undirected_multigraph = nx.MultiGraph()
+        cls.undirected_multigraph.add_node("n10")
+        cls.undirected_multigraph.add_edge("n0", "n2", id="e0")
+        cls.undirected_multigraph.add_edge("n1", "n2", id="e1")
+        cls.undirected_multigraph.add_edge("n2", "n1", id="e2")
+        fh = io.BytesIO(cls.undirected_multigraph_data.encode("UTF-8"))
+        cls.undirected_multigraph_fh = fh
+
+        cls.undirected_multigraph_no_multiedge_data = """<?xml version="1.0" encoding="UTF-8"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <graph id="G">
+    <node id="n0"/>
+    <node id="n1"/>
+    <node id="n2"/>
+    <node id="n10"/>
+    <edge id="e0" source="n0" target="n2"/>
+    <edge id="e1" source="n1" target="n2"/>
+    <edge id="e2" source="n2" target="n3"/>
+  </graph>
+</graphml>"""
+        cls.undirected_multigraph_no_multiedge = nx.MultiGraph()
+        cls.undirected_multigraph_no_multiedge.add_node("n10")
+        cls.undirected_multigraph_no_multiedge.add_edge("n0", "n2", id="e0")
+        cls.undirected_multigraph_no_multiedge.add_edge("n1", "n2", id="e1")
+        cls.undirected_multigraph_no_multiedge.add_edge("n2", "n3", id="e2")
+        fh = io.BytesIO(cls.undirected_multigraph_no_multiedge_data.encode("UTF-8"))
+        cls.undirected_multigraph_no_multiedge_fh = fh
+
+        cls.multigraph_only_ids_for_multiedges_data = """<?xml version="1.0" encoding="UTF-8"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <graph id="G">
+    <node id="n0"/>
+    <node id="n1"/>
+    <node id="n2"/>
+    <node id="n10"/>
+    <edge source="n0" target="n2"/>
+    <edge id="e1" source="n1" target="n2"/>
+    <edge id="e2" source="n2" target="n1"/>
+  </graph>
+</graphml>"""
+        cls.multigraph_only_ids_for_multiedges = nx.MultiGraph()
+        cls.multigraph_only_ids_for_multiedges.add_node("n10")
+        cls.multigraph_only_ids_for_multiedges.add_edge("n0", "n2")
+        cls.multigraph_only_ids_for_multiedges.add_edge("n1", "n2", id="e1")
+        cls.multigraph_only_ids_for_multiedges.add_edge("n2", "n1", id="e2")
+        fh = io.BytesIO(cls.multigraph_only_ids_for_multiedges_data.encode("UTF-8"))
+        cls.multigraph_only_ids_for_multiedges_fh = fh
+
+
+class TestReadGraphML(BaseGraphML):
+    def test_read_simple_directed_graphml(self):
+        G = self.simple_directed_graph
+        H = nx.read_graphml(self.simple_directed_fh)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(G.edges()) == sorted(H.edges())
+        assert sorted(G.edges(data=True)) == sorted(H.edges(data=True))
+        self.simple_directed_fh.seek(0)
+
+        PG = nx.parse_graphml(self.simple_directed_data)
+        assert sorted(G.nodes()) == sorted(PG.nodes())
+        assert sorted(G.edges()) == sorted(PG.edges())
+        assert sorted(G.edges(data=True)) == sorted(PG.edges(data=True))
+
+    def test_read_simple_undirected_graphml(self):
+        G = self.simple_undirected_graph
+        H = nx.read_graphml(self.simple_undirected_fh)
+        assert nodes_equal(G.nodes(), H.nodes())
+        assert edges_equal(G.edges(), H.edges())
+        self.simple_undirected_fh.seek(0)
+
+        PG = nx.parse_graphml(self.simple_undirected_data)
+        assert nodes_equal(G.nodes(), PG.nodes())
+        assert edges_equal(G.edges(), PG.edges())
+
+    def test_read_undirected_multigraph_graphml(self):
+        G = self.undirected_multigraph
+        H = nx.read_graphml(self.undirected_multigraph_fh)
+        assert nodes_equal(G.nodes(), H.nodes())
+        assert edges_equal(G.edges(), H.edges())
+        self.undirected_multigraph_fh.seek(0)
+
+        PG = nx.parse_graphml(self.undirected_multigraph_data)
+        assert nodes_equal(G.nodes(), PG.nodes())
+        assert edges_equal(G.edges(), PG.edges())
+
+    def test_read_undirected_multigraph_no_multiedge_graphml(self):
+        G = self.undirected_multigraph_no_multiedge
+        H = nx.read_graphml(self.undirected_multigraph_no_multiedge_fh)
+        assert nodes_equal(G.nodes(), H.nodes())
+        assert edges_equal(G.edges(), H.edges())
+        self.undirected_multigraph_no_multiedge_fh.seek(0)
+
+        PG = nx.parse_graphml(self.undirected_multigraph_no_multiedge_data)
+        assert nodes_equal(G.nodes(), PG.nodes())
+        assert edges_equal(G.edges(), PG.edges())
+
+    def test_read_undirected_multigraph_only_ids_for_multiedges_graphml(self):
+        G = self.multigraph_only_ids_for_multiedges
+        H = nx.read_graphml(self.multigraph_only_ids_for_multiedges_fh)
+        assert nodes_equal(G.nodes(), H.nodes())
+        assert edges_equal(G.edges(), H.edges())
+        self.multigraph_only_ids_for_multiedges_fh.seek(0)
+
+        PG = nx.parse_graphml(self.multigraph_only_ids_for_multiedges_data)
+        assert nodes_equal(G.nodes(), PG.nodes())
+        assert edges_equal(G.edges(), PG.edges())
+
+    def test_read_attribute_graphml(self):
+        G = self.attribute_graph
+        H = nx.read_graphml(self.attribute_fh)
+        assert nodes_equal(G.nodes(True), sorted(H.nodes(data=True)))
+        ge = sorted(G.edges(data=True))
+        he = sorted(H.edges(data=True))
+        for a, b in zip(ge, he):
+            assert a == b
+        self.attribute_fh.seek(0)
+
+        PG = nx.parse_graphml(self.attribute_data)
+        assert sorted(G.nodes(True)) == sorted(PG.nodes(data=True))
+        ge = sorted(G.edges(data=True))
+        he = sorted(PG.edges(data=True))
+        for a, b in zip(ge, he):
+            assert a == b
+
+    def test_node_default_attribute_graphml(self):
+        G = self.node_attribute_default_graph
+        H = nx.read_graphml(self.node_attribute_default_fh)
+        assert G.graph["node_default"] == H.graph["node_default"]
+
+    def test_directed_edge_in_undirected(self):
+        s = """<?xml version="1.0" encoding="UTF-8"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <graph id="G">
+    <node id="n0"/>
+    <node id="n1"/>
+    <node id="n2"/>
+    <edge source="n0" target="n1"/>
+    <edge source="n1" target="n2" directed='true'/>
+  </graph>
+</graphml>"""
+        fh = io.BytesIO(s.encode("UTF-8"))
+        pytest.raises(nx.NetworkXError, nx.read_graphml, fh)
+        pytest.raises(nx.NetworkXError, nx.parse_graphml, s)
+
+    def test_undirected_edge_in_directed(self):
+        s = """<?xml version="1.0" encoding="UTF-8"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <graph id="G" edgedefault='directed'>
+    <node id="n0"/>
+    <node id="n1"/>
+    <node id="n2"/>
+    <edge source="n0" target="n1"/>
+    <edge source="n1" target="n2" directed='false'/>
+  </graph>
+</graphml>"""
+        fh = io.BytesIO(s.encode("UTF-8"))
+        pytest.raises(nx.NetworkXError, nx.read_graphml, fh)
+        pytest.raises(nx.NetworkXError, nx.parse_graphml, s)
+
+    def test_key_raise(self):
+        s = """<?xml version="1.0" encoding="UTF-8"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <key id="d0" for="node" attr.name="color" attr.type="string">
+    <default>yellow</default>
+  </key>
+  <key id="d1" for="edge" attr.name="weight" attr.type="double"/>
+  <graph id="G" edgedefault="directed">
+    <node id="n0">
+      <data key="d0">green</data>
+    </node>
+    <node id="n1"/>
+    <node id="n2">
+      <data key="d0">blue</data>
+    </node>
+    <edge id="e0" source="n0" target="n2">
+      <data key="d2">1.0</data>
+    </edge>
+  </graph>
+</graphml>
+"""
+        fh = io.BytesIO(s.encode("UTF-8"))
+        pytest.raises(nx.NetworkXError, nx.read_graphml, fh)
+        pytest.raises(nx.NetworkXError, nx.parse_graphml, s)
+
+    def test_hyperedge_raise(self):
+        s = """<?xml version="1.0" encoding="UTF-8"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <key id="d0" for="node" attr.name="color" attr.type="string">
+    <default>yellow</default>
+  </key>
+  <key id="d1" for="edge" attr.name="weight" attr.type="double"/>
+  <graph id="G" edgedefault="directed">
+    <node id="n0">
+      <data key="d0">green</data>
+    </node>
+    <node id="n1"/>
+    <node id="n2">
+      <data key="d0">blue</data>
+    </node>
+    <hyperedge id="e0" source="n0" target="n2">
+       <endpoint node="n0"/>
+       <endpoint node="n1"/>
+       <endpoint node="n2"/>
+    </hyperedge>
+  </graph>
+</graphml>
+"""
+        fh = io.BytesIO(s.encode("UTF-8"))
+        pytest.raises(nx.NetworkXError, nx.read_graphml, fh)
+        pytest.raises(nx.NetworkXError, nx.parse_graphml, s)
+
+    def test_multigraph_keys(self):
+        # Test that reading multigraphs uses edge id attributes as keys
+        s = """<?xml version="1.0" encoding="UTF-8"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <graph id="G" edgedefault="directed">
+    <node id="n0"/>
+    <node id="n1"/>
+    <edge id="e0" source="n0" target="n1"/>
+    <edge id="e1" source="n0" target="n1"/>
+  </graph>
+</graphml>
+"""
+        fh = io.BytesIO(s.encode("UTF-8"))
+        G = nx.read_graphml(fh)
+        expected = [("n0", "n1", "e0"), ("n0", "n1", "e1")]
+        assert sorted(G.edges(keys=True)) == expected
+        fh.seek(0)
+        H = nx.parse_graphml(s)
+        assert sorted(H.edges(keys=True)) == expected
+
+    def test_preserve_multi_edge_data(self):
+        """
+        Test that data and keys of edges are preserved on consequent
+        write and reads
+        """
+        G = nx.MultiGraph()
+        G.add_node(1)
+        G.add_node(2)
+        G.add_edges_from(
+            [
+                # edges with no data, no keys:
+                (1, 2),
+                # edges with only data:
+                (1, 2, {"key": "data_key1"}),
+                (1, 2, {"id": "data_id2"}),
+                (1, 2, {"key": "data_key3", "id": "data_id3"}),
+                # edges with both data and keys:
+                (1, 2, 103, {"key": "data_key4"}),
+                (1, 2, 104, {"id": "data_id5"}),
+                (1, 2, 105, {"key": "data_key6", "id": "data_id7"}),
+            ]
+        )
+        fh = io.BytesIO()
+        nx.write_graphml(G, fh)
+        fh.seek(0)
+        H = nx.read_graphml(fh, node_type=int)
+        assert edges_equal(G.edges(data=True, keys=True), H.edges(data=True, keys=True))
+        assert G._adj == H._adj
+
+        Gadj = {
+            str(node): {
+                str(nbr): {str(ekey): dd for ekey, dd in key_dict.items()}
+                for nbr, key_dict in nbr_dict.items()
+            }
+            for node, nbr_dict in G._adj.items()
+        }
+        fh.seek(0)
+        HH = nx.read_graphml(fh, node_type=str, edge_key_type=str)
+        assert Gadj == HH._adj
+
+        fh.seek(0)
+        string_fh = fh.read()
+        HH = nx.parse_graphml(string_fh, node_type=str, edge_key_type=str)
+        assert Gadj == HH._adj
+
+    def test_yfiles_extension(self):
+        data = """<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xmlns:y="http://www.yworks.com/xml/graphml"
+         xmlns:yed="http://www.yworks.com/xml/yed/3"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <!--Created by yFiles for Java 2.7-->
+  <key for="graphml" id="d0" yfiles.type="resources"/>
+  <key attr.name="url" attr.type="string" for="node" id="d1"/>
+  <key attr.name="description" attr.type="string" for="node" id="d2"/>
+  <key for="node" id="d3" yfiles.type="nodegraphics"/>
+  <key attr.name="Description" attr.type="string" for="graph" id="d4">
+    <default/>
+  </key>
+  <key attr.name="url" attr.type="string" for="edge" id="d5"/>
+  <key attr.name="description" attr.type="string" for="edge" id="d6"/>
+  <key for="edge" id="d7" yfiles.type="edgegraphics"/>
+  <graph edgedefault="directed" id="G">
+    <node id="n0">
+      <data key="d3">
+        <y:ShapeNode>
+          <y:Geometry height="30.0" width="30.0" x="125.0" y="100.0"/>
+          <y:Fill color="#FFCC00" transparent="false"/>
+          <y:BorderStyle color="#000000" type="line" width="1.0"/>
+          <y:NodeLabel alignment="center" autoSizePolicy="content"
+           borderDistance="0.0" fontFamily="Dialog" fontSize="13"
+           fontStyle="plain" hasBackgroundColor="false" hasLineColor="false"
+           height="19.1328125" modelName="internal" modelPosition="c"
+           textColor="#000000" visible="true" width="12.27099609375"
+           x="8.864501953125" y="5.43359375">1</y:NodeLabel>
+          <y:Shape type="rectangle"/>
+        </y:ShapeNode>
+      </data>
+    </node>
+    <node id="n1">
+      <data key="d3">
+        <y:ShapeNode>
+          <y:Geometry height="30.0" width="30.0" x="183.0" y="205.0"/>
+          <y:Fill color="#FFCC00" transparent="false"/>
+          <y:BorderStyle color="#000000" type="line" width="1.0"/>
+          <y:NodeLabel alignment="center" autoSizePolicy="content"
+          borderDistance="0.0" fontFamily="Dialog" fontSize="13"
+          fontStyle="plain" hasBackgroundColor="false" hasLineColor="false"
+          height="19.1328125" modelName="internal" modelPosition="c"
+          textColor="#000000" visible="true" width="12.27099609375"
+          x="8.864501953125" y="5.43359375">2</y:NodeLabel>
+          <y:Shape type="rectangle"/>
+        </y:ShapeNode>
+      </data>
+    </node>
+    <node id="n2">
+      <data key="d6" xml:space="preserve"><![CDATA[description
+line1
+line2]]></data>
+      <data key="d3">
+        <y:GenericNode configuration="com.yworks.flowchart.terminator">
+          <y:Geometry height="40.0" width="80.0" x="950.0" y="286.0"/>
+          <y:Fill color="#E8EEF7" color2="#B7C9E3" transparent="false"/>
+          <y:BorderStyle color="#000000" type="line" width="1.0"/>
+          <y:NodeLabel alignment="center" autoSizePolicy="content"
+          fontFamily="Dialog" fontSize="12" fontStyle="plain"
+          hasBackgroundColor="false" hasLineColor="false" height="17.96875"
+          horizontalTextPosition="center" iconTextGap="4" modelName="custom"
+          textColor="#000000" verticalTextPosition="bottom" visible="true"
+          width="67.984375" x="6.0078125" xml:space="preserve"
+          y="11.015625">3<y:LabelModel>
+          <y:SmartNodeLabelModel distance="4.0"/></y:LabelModel>
+          <y:ModelParameter><y:SmartNodeLabelModelParameter labelRatioX="0.0"
+          labelRatioY="0.0" nodeRatioX="0.0" nodeRatioY="0.0" offsetX="0.0"
+          offsetY="0.0" upX="0.0" upY="-1.0"/></y:ModelParameter></y:NodeLabel>
+        </y:GenericNode>
+      </data>
+    </node>
+    <edge id="e0" source="n0" target="n1">
+      <data key="d7">
+        <y:PolyLineEdge>
+          <y:Path sx="0.0" sy="0.0" tx="0.0" ty="0.0"/>
+          <y:LineStyle color="#000000" type="line" width="1.0"/>
+          <y:Arrows source="none" target="standard"/>
+          <y:BendStyle smoothed="false"/>
+        </y:PolyLineEdge>
+      </data>
+    </edge>
+  </graph>
+  <data key="d0">
+    <y:Resources/>
+  </data>
+</graphml>
+"""
+        fh = io.BytesIO(data.encode("UTF-8"))
+        G = nx.read_graphml(fh, force_multigraph=True)
+        assert list(G.edges()) == [("n0", "n1")]
+        assert G.has_edge("n0", "n1", key="e0")
+        assert G.nodes["n0"]["label"] == "1"
+        assert G.nodes["n1"]["label"] == "2"
+        assert G.nodes["n2"]["label"] == "3"
+        assert G.nodes["n0"]["shape_type"] == "rectangle"
+        assert G.nodes["n1"]["shape_type"] == "rectangle"
+        assert G.nodes["n2"]["shape_type"] == "com.yworks.flowchart.terminator"
+        assert G.nodes["n2"]["description"] == "description\nline1\nline2"
+        fh.seek(0)
+        G = nx.read_graphml(fh)
+        assert list(G.edges()) == [("n0", "n1")]
+        assert G["n0"]["n1"]["id"] == "e0"
+        assert G.nodes["n0"]["label"] == "1"
+        assert G.nodes["n1"]["label"] == "2"
+        assert G.nodes["n2"]["label"] == "3"
+        assert G.nodes["n0"]["shape_type"] == "rectangle"
+        assert G.nodes["n1"]["shape_type"] == "rectangle"
+        assert G.nodes["n2"]["shape_type"] == "com.yworks.flowchart.terminator"
+        assert G.nodes["n2"]["description"] == "description\nline1\nline2"
+
+        H = nx.parse_graphml(data, force_multigraph=True)
+        assert list(H.edges()) == [("n0", "n1")]
+        assert H.has_edge("n0", "n1", key="e0")
+        assert H.nodes["n0"]["label"] == "1"
+        assert H.nodes["n1"]["label"] == "2"
+        assert H.nodes["n2"]["label"] == "3"
+
+        H = nx.parse_graphml(data)
+        assert list(H.edges()) == [("n0", "n1")]
+        assert H["n0"]["n1"]["id"] == "e0"
+        assert H.nodes["n0"]["label"] == "1"
+        assert H.nodes["n1"]["label"] == "2"
+        assert H.nodes["n2"]["label"] == "3"
+
+    def test_bool(self):
+        s = """<?xml version="1.0" encoding="UTF-8"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <key id="d0" for="node" attr.name="test" attr.type="boolean">
+    <default>false</default>
+  </key>
+  <graph id="G" edgedefault="directed">
+    <node id="n0">
+      <data key="d0">true</data>
+    </node>
+    <node id="n1"/>
+    <node id="n2">
+      <data key="d0">false</data>
+    </node>
+    <node id="n3">
+      <data key="d0">FaLsE</data>
+    </node>
+    <node id="n4">
+      <data key="d0">True</data>
+    </node>
+    <node id="n5">
+      <data key="d0">0</data>
+    </node>
+    <node id="n6">
+      <data key="d0">1</data>
+    </node>
+  </graph>
+</graphml>
+"""
+        fh = io.BytesIO(s.encode("UTF-8"))
+        G = nx.read_graphml(fh)
+        H = nx.parse_graphml(s)
+        for graph in [G, H]:
+            assert graph.nodes["n0"]["test"]
+            assert not graph.nodes["n2"]["test"]
+            assert not graph.nodes["n3"]["test"]
+            assert graph.nodes["n4"]["test"]
+            assert not graph.nodes["n5"]["test"]
+            assert graph.nodes["n6"]["test"]
+
+    def test_graphml_header_line(self):
+        good = """<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <key id="d0" for="node" attr.name="test" attr.type="boolean">
+    <default>false</default>
+  </key>
+  <graph id="G">
+    <node id="n0">
+      <data key="d0">true</data>
+    </node>
+  </graph>
+</graphml>
+"""
+        bad = """<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<graphml>
+  <key id="d0" for="node" attr.name="test" attr.type="boolean">
+    <default>false</default>
+  </key>
+  <graph id="G">
+    <node id="n0">
+      <data key="d0">true</data>
+    </node>
+  </graph>
+</graphml>
+"""
+        ugly = """<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<graphml xmlns="https://ghghgh">
+  <key id="d0" for="node" attr.name="test" attr.type="boolean">
+    <default>false</default>
+  </key>
+  <graph id="G">
+    <node id="n0">
+      <data key="d0">true</data>
+    </node>
+  </graph>
+</graphml>
+"""
+        for s in (good, bad):
+            fh = io.BytesIO(s.encode("UTF-8"))
+            G = nx.read_graphml(fh)
+            H = nx.parse_graphml(s)
+            for graph in [G, H]:
+                assert graph.nodes["n0"]["test"]
+
+        fh = io.BytesIO(ugly.encode("UTF-8"))
+        pytest.raises(nx.NetworkXError, nx.read_graphml, fh)
+        pytest.raises(nx.NetworkXError, nx.parse_graphml, ugly)
+
+    def test_read_attributes_with_groups(self):
+        data = """\
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns" xmlns:java="http://www.yworks.com/xml/yfiles-common/1.0/java" xmlns:sys="http://www.yworks.com/xml/yfiles-common/markup/primitives/2.0" xmlns:x="http://www.yworks.com/xml/yfiles-common/markup/2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:y="http://www.yworks.com/xml/graphml" xmlns:yed="http://www.yworks.com/xml/yed/3" xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns http://www.yworks.com/xml/schema/graphml/1.1/ygraphml.xsd">
+  <!--Created by yEd 3.17-->
+  <key attr.name="Description" attr.type="string" for="graph" id="d0"/>
+  <key for="port" id="d1" yfiles.type="portgraphics"/>
+  <key for="port" id="d2" yfiles.type="portgeometry"/>
+  <key for="port" id="d3" yfiles.type="portuserdata"/>
+  <key attr.name="CustomProperty" attr.type="string" for="node" id="d4">
+    <default/>
+  </key>
+  <key attr.name="url" attr.type="string" for="node" id="d5"/>
+  <key attr.name="description" attr.type="string" for="node" id="d6"/>
+  <key for="node" id="d7" yfiles.type="nodegraphics"/>
+  <key for="graphml" id="d8" yfiles.type="resources"/>
+  <key attr.name="url" attr.type="string" for="edge" id="d9"/>
+  <key attr.name="description" attr.type="string" for="edge" id="d10"/>
+  <key for="edge" id="d11" yfiles.type="edgegraphics"/>
+  <graph edgedefault="directed" id="G">
+    <data key="d0"/>
+    <node id="n0">
+      <data key="d4"><![CDATA[CustomPropertyValue]]></data>
+      <data key="d6"/>
+      <data key="d7">
+        <y:ShapeNode>
+          <y:Geometry height="30.0" width="30.0" x="125.0" y="-255.4611111111111"/>
+          <y:Fill color="#FFCC00" transparent="false"/>
+          <y:BorderStyle color="#000000" raised="false" type="line" width="1.0"/>
+          <y:NodeLabel alignment="center" autoSizePolicy="content" fontFamily="Dialog" fontSize="12" fontStyle="plain" hasBackgroundColor="false" hasLineColor="false" height="17.96875" horizontalTextPosition="center" iconTextGap="4" modelName="custom" textColor="#000000" verticalTextPosition="bottom" visible="true" width="11.634765625" x="9.1826171875" y="6.015625">2<y:LabelModel>
+              <y:SmartNodeLabelModel distance="4.0"/>
+            </y:LabelModel>
+            <y:ModelParameter>
+              <y:SmartNodeLabelModelParameter labelRatioX="0.0" labelRatioY="0.0" nodeRatioX="0.0" nodeRatioY="0.0" offsetX="0.0" offsetY="0.0" upX="0.0" upY="-1.0"/>
+            </y:ModelParameter>
+          </y:NodeLabel>
+          <y:Shape type="rectangle"/>
+        </y:ShapeNode>
+      </data>
+    </node>
+    <node id="n1" yfiles.foldertype="group">
+      <data key="d4"><![CDATA[CustomPropertyValue]]></data>
+      <data key="d5"/>
+      <data key="d6"/>
+      <data key="d7">
+        <y:ProxyAutoBoundsNode>
+          <y:Realizers active="0">
+            <y:GroupNode>
+              <y:Geometry height="250.38333333333333" width="140.0" x="-30.0" y="-330.3833333333333"/>
+              <y:Fill color="#F5F5F5" transparent="false"/>
+              <y:BorderStyle color="#000000" type="dashed" width="1.0"/>
+              <y:NodeLabel alignment="right" autoSizePolicy="node_width" backgroundColor="#EBEBEB" borderDistance="0.0" fontFamily="Dialog" fontSize="15" fontStyle="plain" hasLineColor="false" height="21.4609375" horizontalTextPosition="center" iconTextGap="4" modelName="internal" modelPosition="t" textColor="#000000" verticalTextPosition="bottom" visible="true" width="140.0" x="0.0" y="0.0">Group 3</y:NodeLabel>
+              <y:Shape type="roundrectangle"/>
+              <y:State closed="false" closedHeight="50.0" closedWidth="50.0" innerGraphDisplayEnabled="false"/>
+              <y:Insets bottom="15" bottomF="15.0" left="15" leftF="15.0" right="15" rightF="15.0" top="15" topF="15.0"/>
+              <y:BorderInsets bottom="1" bottomF="1.0" left="0" leftF="0.0" right="0" rightF="0.0" top="1" topF="1.0001736111111086"/>
+            </y:GroupNode>
+            <y:GroupNode>
+              <y:Geometry height="50.0" width="50.0" x="0.0" y="60.0"/>
+              <y:Fill color="#F5F5F5" transparent="false"/>
+              <y:BorderStyle color="#000000" type="dashed" width="1.0"/>
+              <y:NodeLabel alignment="right" autoSizePolicy="node_width" backgroundColor="#EBEBEB" borderDistance="0.0" fontFamily="Dialog" fontSize="15" fontStyle="plain" hasLineColor="false" height="21.4609375" horizontalTextPosition="center" iconTextGap="4" modelName="internal" modelPosition="t" textColor="#000000" verticalTextPosition="bottom" visible="true" width="65.201171875" x="-7.6005859375" y="0.0">Folder 3</y:NodeLabel>
+              <y:Shape type="roundrectangle"/>
+              <y:State closed="true" closedHeight="50.0" closedWidth="50.0" innerGraphDisplayEnabled="false"/>
+              <y:Insets bottom="5" bottomF="5.0" left="5" leftF="5.0" right="5" rightF="5.0" top="5" topF="5.0"/>
+              <y:BorderInsets bottom="0" bottomF="0.0" left="0" leftF="0.0" right="0" rightF="0.0" top="0" topF="0.0"/>
+            </y:GroupNode>
+          </y:Realizers>
+        </y:ProxyAutoBoundsNode>
+      </data>
+      <graph edgedefault="directed" id="n1:">
+        <node id="n1::n0" yfiles.foldertype="group">
+          <data key="d4"><![CDATA[CustomPropertyValue]]></data>
+          <data key="d5"/>
+          <data key="d6"/>
+          <data key="d7">
+            <y:ProxyAutoBoundsNode>
+              <y:Realizers active="0">
+                <y:GroupNode>
+                  <y:Geometry height="83.46111111111111" width="110.0" x="-15.0" y="-292.9222222222222"/>
+                  <y:Fill color="#F5F5F5" transparent="false"/>
+                  <y:BorderStyle color="#000000" type="dashed" width="1.0"/>
+                  <y:NodeLabel alignment="right" autoSizePolicy="node_width" backgroundColor="#EBEBEB" borderDistance="0.0" fontFamily="Dialog" fontSize="15" fontStyle="plain" hasLineColor="false" height="21.4609375" horizontalTextPosition="center" iconTextGap="4" modelName="internal" modelPosition="t" textColor="#000000" verticalTextPosition="bottom" visible="true" width="110.0" x="0.0" y="0.0">Group 1</y:NodeLabel>
+                  <y:Shape type="roundrectangle"/>
+                  <y:State closed="false" closedHeight="50.0" closedWidth="50.0" innerGraphDisplayEnabled="false"/>
+                  <y:Insets bottom="15" bottomF="15.0" left="15" leftF="15.0" right="15" rightF="15.0" top="15" topF="15.0"/>
+                  <y:BorderInsets bottom="1" bottomF="1.0" left="0" leftF="0.0" right="0" rightF="0.0" top="1" topF="1.0001736111111086"/>
+                </y:GroupNode>
+                <y:GroupNode>
+                  <y:Geometry height="50.0" width="50.0" x="0.0" y="60.0"/>
+                  <y:Fill color="#F5F5F5" transparent="false"/>
+                  <y:BorderStyle color="#000000" type="dashed" width="1.0"/>
+                  <y:NodeLabel alignment="right" autoSizePolicy="node_width" backgroundColor="#EBEBEB" borderDistance="0.0" fontFamily="Dialog" fontSize="15" fontStyle="plain" hasLineColor="false" height="21.4609375" horizontalTextPosition="center" iconTextGap="4" modelName="internal" modelPosition="t" textColor="#000000" verticalTextPosition="bottom" visible="true" width="65.201171875" x="-7.6005859375" y="0.0">Folder 1</y:NodeLabel>
+                  <y:Shape type="roundrectangle"/>
+                  <y:State closed="true" closedHeight="50.0" closedWidth="50.0" innerGraphDisplayEnabled="false"/>
+                  <y:Insets bottom="5" bottomF="5.0" left="5" leftF="5.0" right="5" rightF="5.0" top="5" topF="5.0"/>
+                  <y:BorderInsets bottom="0" bottomF="0.0" left="0" leftF="0.0" right="0" rightF="0.0" top="0" topF="0.0"/>
+                </y:GroupNode>
+              </y:Realizers>
+            </y:ProxyAutoBoundsNode>
+          </data>
+          <graph edgedefault="directed" id="n1::n0:">
+            <node id="n1::n0::n0">
+              <data key="d4"><![CDATA[CustomPropertyValue]]></data>
+              <data key="d6"/>
+              <data key="d7">
+                <y:ShapeNode>
+                  <y:Geometry height="30.0" width="30.0" x="50.0" y="-255.4611111111111"/>
+                  <y:Fill color="#FFCC00" transparent="false"/>
+                  <y:BorderStyle color="#000000" raised="false" type="line" width="1.0"/>
+                  <y:NodeLabel alignment="center" autoSizePolicy="content" fontFamily="Dialog" fontSize="12" fontStyle="plain" hasBackgroundColor="false" hasLineColor="false" height="17.96875" horizontalTextPosition="center" iconTextGap="4" modelName="custom" textColor="#000000" verticalTextPosition="bottom" visible="true" width="11.634765625" x="9.1826171875" y="6.015625">1<y:LabelModel>
+                      <y:SmartNodeLabelModel distance="4.0"/>
+                    </y:LabelModel>
+                    <y:ModelParameter>
+                      <y:SmartNodeLabelModelParameter labelRatioX="0.0" labelRatioY="0.0" nodeRatioX="0.0" nodeRatioY="0.0" offsetX="0.0" offsetY="0.0" upX="0.0" upY="-1.0"/>
+                    </y:ModelParameter>
+                  </y:NodeLabel>
+                  <y:Shape type="rectangle"/>
+                </y:ShapeNode>
+              </data>
+            </node>
+            <node id="n1::n0::n1">
+              <data key="d4"><![CDATA[CustomPropertyValue]]></data>
+              <data key="d6"/>
+              <data key="d7">
+                <y:ShapeNode>
+                  <y:Geometry height="30.0" width="30.0" x="0.0" y="-255.4611111111111"/>
+                  <y:Fill color="#FFCC00" transparent="false"/>
+                  <y:BorderStyle color="#000000" raised="false" type="line" width="1.0"/>
+                  <y:NodeLabel alignment="center" autoSizePolicy="content" fontFamily="Dialog" fontSize="12" fontStyle="plain" hasBackgroundColor="false" hasLineColor="false" height="17.96875" horizontalTextPosition="center" iconTextGap="4" modelName="custom" textColor="#000000" verticalTextPosition="bottom" visible="true" width="11.634765625" x="9.1826171875" y="6.015625">3<y:LabelModel>
+                      <y:SmartNodeLabelModel distance="4.0"/>
+                    </y:LabelModel>
+                    <y:ModelParameter>
+                      <y:SmartNodeLabelModelParameter labelRatioX="0.0" labelRatioY="0.0" nodeRatioX="0.0" nodeRatioY="0.0" offsetX="0.0" offsetY="0.0" upX="0.0" upY="-1.0"/>
+                    </y:ModelParameter>
+                  </y:NodeLabel>
+                  <y:Shape type="rectangle"/>
+                </y:ShapeNode>
+              </data>
+            </node>
+          </graph>
+        </node>
+        <node id="n1::n1" yfiles.foldertype="group">
+          <data key="d4"><![CDATA[CustomPropertyValue]]></data>
+          <data key="d5"/>
+          <data key="d6"/>
+          <data key="d7">
+            <y:ProxyAutoBoundsNode>
+              <y:Realizers active="0">
+                <y:GroupNode>
+                  <y:Geometry height="83.46111111111111" width="110.0" x="-15.0" y="-179.4611111111111"/>
+                  <y:Fill color="#F5F5F5" transparent="false"/>
+                  <y:BorderStyle color="#000000" type="dashed" width="1.0"/>
+                  <y:NodeLabel alignment="right" autoSizePolicy="node_width" backgroundColor="#EBEBEB" borderDistance="0.0" fontFamily="Dialog" fontSize="15" fontStyle="plain" hasLineColor="false" height="21.4609375" horizontalTextPosition="center" iconTextGap="4" modelName="internal" modelPosition="t" textColor="#000000" verticalTextPosition="bottom" visible="true" width="110.0" x="0.0" y="0.0">Group 2</y:NodeLabel>
+                  <y:Shape type="roundrectangle"/>
+                  <y:State closed="false" closedHeight="50.0" closedWidth="50.0" innerGraphDisplayEnabled="false"/>
+                  <y:Insets bottom="15" bottomF="15.0" left="15" leftF="15.0" right="15" rightF="15.0" top="15" topF="15.0"/>
+                  <y:BorderInsets bottom="1" bottomF="1.0" left="0" leftF="0.0" right="0" rightF="0.0" top="1" topF="1.0001736111111086"/>
+                </y:GroupNode>
+                <y:GroupNode>
+                  <y:Geometry height="50.0" width="50.0" x="0.0" y="60.0"/>
+                  <y:Fill color="#F5F5F5" transparent="false"/>
+                  <y:BorderStyle color="#000000" type="dashed" width="1.0"/>
+                  <y:NodeLabel alignment="right" autoSizePolicy="node_width" backgroundColor="#EBEBEB" borderDistance="0.0" fontFamily="Dialog" fontSize="15" fontStyle="plain" hasLineColor="false" height="21.4609375" horizontalTextPosition="center" iconTextGap="4" modelName="internal" modelPosition="t" textColor="#000000" verticalTextPosition="bottom" visible="true" width="65.201171875" x="-7.6005859375" y="0.0">Folder 2</y:NodeLabel>
+                  <y:Shape type="roundrectangle"/>
+                  <y:State closed="true" closedHeight="50.0" closedWidth="50.0" innerGraphDisplayEnabled="false"/>
+                  <y:Insets bottom="5" bottomF="5.0" left="5" leftF="5.0" right="5" rightF="5.0" top="5" topF="5.0"/>
+                  <y:BorderInsets bottom="0" bottomF="0.0" left="0" leftF="0.0" right="0" rightF="0.0" top="0" topF="0.0"/>
+                </y:GroupNode>
+              </y:Realizers>
+            </y:ProxyAutoBoundsNode>
+          </data>
+          <graph edgedefault="directed" id="n1::n1:">
+            <node id="n1::n1::n0">
+              <data key="d4"><![CDATA[CustomPropertyValue]]></data>
+              <data key="d6"/>
+              <data key="d7">
+                <y:ShapeNode>
+                  <y:Geometry height="30.0" width="30.0" x="0.0" y="-142.0"/>
+                  <y:Fill color="#FFCC00" transparent="false"/>
+                  <y:BorderStyle color="#000000" raised="false" type="line" width="1.0"/>
+                  <y:NodeLabel alignment="center" autoSizePolicy="content" fontFamily="Dialog" fontSize="12" fontStyle="plain" hasBackgroundColor="false" hasLineColor="false" height="17.96875" horizontalTextPosition="center" iconTextGap="4" modelName="custom" textColor="#000000" verticalTextPosition="bottom" visible="true" width="11.634765625" x="9.1826171875" y="6.015625">5<y:LabelModel>
+                      <y:SmartNodeLabelModel distance="4.0"/>
+                    </y:LabelModel>
+                    <y:ModelParameter>
+                      <y:SmartNodeLabelModelParameter labelRatioX="0.0" labelRatioY="0.0" nodeRatioX="0.0" nodeRatioY="0.0" offsetX="0.0" offsetY="0.0" upX="0.0" upY="-1.0"/>
+                    </y:ModelParameter>
+                  </y:NodeLabel>
+                  <y:Shape type="rectangle"/>
+                </y:ShapeNode>
+              </data>
+            </node>
+            <node id="n1::n1::n1">
+              <data key="d4"><![CDATA[CustomPropertyValue]]></data>
+              <data key="d6"/>
+              <data key="d7">
+                <y:ShapeNode>
+                  <y:Geometry height="30.0" width="30.0" x="50.0" y="-142.0"/>
+                  <y:Fill color="#FFCC00" transparent="false"/>
+                  <y:BorderStyle color="#000000" raised="false" type="line" width="1.0"/>
+                  <y:NodeLabel alignment="center" autoSizePolicy="content" fontFamily="Dialog" fontSize="12" fontStyle="plain" hasBackgroundColor="false" hasLineColor="false" height="17.96875" horizontalTextPosition="center" iconTextGap="4" modelName="custom" textColor="#000000" verticalTextPosition="bottom" visible="true" width="11.634765625" x="9.1826171875" y="6.015625">6<y:LabelModel>
+                      <y:SmartNodeLabelModel distance="4.0"/>
+                    </y:LabelModel>
+                    <y:ModelParameter>
+                      <y:SmartNodeLabelModelParameter labelRatioX="0.0" labelRatioY="0.0" nodeRatioX="0.0" nodeRatioY="0.0" offsetX="0.0" offsetY="0.0" upX="0.0" upY="-1.0"/>
+                    </y:ModelParameter>
+                  </y:NodeLabel>
+                  <y:Shape type="rectangle"/>
+                </y:ShapeNode>
+              </data>
+            </node>
+          </graph>
+        </node>
+      </graph>
+    </node>
+    <node id="n2">
+      <data key="d4"><![CDATA[CustomPropertyValue]]></data>
+      <data key="d6"/>
+      <data key="d7">
+        <y:ShapeNode>
+          <y:Geometry height="30.0" width="30.0" x="125.0" y="-142.0"/>
+          <y:Fill color="#FFCC00" transparent="false"/>
+          <y:BorderStyle color="#000000" raised="false" type="line" width="1.0"/>
+          <y:NodeLabel alignment="center" autoSizePolicy="content" fontFamily="Dialog" fontSize="12" fontStyle="plain" hasBackgroundColor="false" hasLineColor="false" height="17.96875" horizontalTextPosition="center" iconTextGap="4" modelName="custom" textColor="#000000" verticalTextPosition="bottom" visible="true" width="11.634765625" x="9.1826171875" y="6.015625">9<y:LabelModel>
+              <y:SmartNodeLabelModel distance="4.0"/>
+            </y:LabelModel>
+            <y:ModelParameter>
+              <y:SmartNodeLabelModelParameter labelRatioX="0.0" labelRatioY="0.0" nodeRatioX="0.0" nodeRatioY="0.0" offsetX="0.0" offsetY="0.0" upX="0.0" upY="-1.0"/>
+            </y:ModelParameter>
+          </y:NodeLabel>
+          <y:Shape type="rectangle"/>
+        </y:ShapeNode>
+      </data>
+    </node>
+    <edge id="n1::n1::e0" source="n1::n1::n0" target="n1::n1::n1">
+      <data key="d10"/>
+      <data key="d11">
+        <y:PolyLineEdge>
+          <y:Path sx="15.0" sy="-0.0" tx="-15.0" ty="-0.0"/>
+          <y:LineStyle color="#000000" type="line" width="1.0"/>
+          <y:Arrows source="none" target="standard"/>
+          <y:BendStyle smoothed="false"/>
+        </y:PolyLineEdge>
+      </data>
+    </edge>
+    <edge id="n1::n0::e0" source="n1::n0::n1" target="n1::n0::n0">
+      <data key="d10"/>
+      <data key="d11">
+        <y:PolyLineEdge>
+          <y:Path sx="15.0" sy="-0.0" tx="-15.0" ty="-0.0"/>
+          <y:LineStyle color="#000000" type="line" width="1.0"/>
+          <y:Arrows source="none" target="standard"/>
+          <y:BendStyle smoothed="false"/>
+        </y:PolyLineEdge>
+      </data>
+    </edge>
+    <edge id="e0" source="n1::n0::n0" target="n0">
+      <data key="d10"/>
+      <data key="d11">
+        <y:PolyLineEdge>
+          <y:Path sx="15.0" sy="-0.0" tx="-15.0" ty="-0.0"/>
+          <y:LineStyle color="#000000" type="line" width="1.0"/>
+          <y:Arrows source="none" target="standard"/>
+          <y:BendStyle smoothed="false"/>
+        </y:PolyLineEdge>
+      </data>
+    </edge>
+    <edge id="e1" source="n1::n1::n1" target="n2">
+      <data key="d10"/>
+      <data key="d11">
+        <y:PolyLineEdge>
+          <y:Path sx="15.0" sy="-0.0" tx="-15.0" ty="-0.0"/>
+          <y:LineStyle color="#000000" type="line" width="1.0"/>
+          <y:Arrows source="none" target="standard"/>
+          <y:BendStyle smoothed="false"/>
+        </y:PolyLineEdge>
+      </data>
+    </edge>
+  </graph>
+  <data key="d8">
+    <y:Resources/>
+  </data>
+</graphml>
+"""
+        # verify that nodes / attributes are correctly read when part of a group
+        fh = io.BytesIO(data.encode("UTF-8"))
+        G = nx.read_graphml(fh)
+        data = [x for _, x in G.nodes(data=True)]
+        assert len(data) == 9
+        for node_data in data:
+            assert node_data["CustomProperty"] != ""
+
+    def test_long_attribute_type(self):
+        # test that graphs with attr.type="long" (as produced by botch and
+        # dose3) can be parsed
+        s = """<?xml version='1.0' encoding='utf-8'?>
+<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
+         http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
+  <key attr.name="cudfversion" attr.type="long" for="node" id="d6" />
+  <graph edgedefault="directed">
+    <node id="n1">
+      <data key="d6">4284</data>
+    </node>
+  </graph>
+</graphml>"""
+        fh = io.BytesIO(s.encode("UTF-8"))
+        G = nx.read_graphml(fh)
+        expected = [("n1", {"cudfversion": 4284})]
+        assert sorted(G.nodes(data=True)) == expected
+        fh.seek(0)
+        H = nx.parse_graphml(s)
+        assert sorted(H.nodes(data=True)) == expected
+
+
+class TestWriteGraphML(BaseGraphML):
+    writer = staticmethod(nx.write_graphml_lxml)
+
+    @classmethod
+    def setup_class(cls):
+        BaseGraphML.setup_class()
+        _ = pytest.importorskip("lxml.etree")
+
+    def test_write_interface(self):
+        try:
+            import lxml.etree
+
+            assert nx.write_graphml == nx.write_graphml_lxml
+        except ImportError:
+            assert nx.write_graphml == nx.write_graphml_xml
+
+    def test_write_read_simple_directed_graphml(self):
+        G = self.simple_directed_graph
+        G.graph["hi"] = "there"
+        fh = io.BytesIO()
+        self.writer(G, fh)
+        fh.seek(0)
+        H = nx.read_graphml(fh)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(G.edges()) == sorted(H.edges())
+        assert sorted(G.edges(data=True)) == sorted(H.edges(data=True))
+        self.simple_directed_fh.seek(0)
+
+    def test_GraphMLWriter_add_graphs(self):
+        gmlw = GraphMLWriter()
+        G = self.simple_directed_graph
+        H = G.copy()
+        gmlw.add_graphs([G, H])
+
+    def test_write_read_simple_no_prettyprint(self):
+        G = self.simple_directed_graph
+        G.graph["hi"] = "there"
+        G.graph["id"] = "1"
+        fh = io.BytesIO()
+        self.writer(G, fh, prettyprint=False)
+        fh.seek(0)
+        H = nx.read_graphml(fh)
+        assert sorted(G.nodes()) == sorted(H.nodes())
+        assert sorted(G.edges()) == sorted(H.edges())
+        assert sorted(G.edges(data=True)) == sorted(H.edges(data=True))
+        self.simple_directed_fh.seek(0)
+
+    def test_write_read_attribute_named_key_ids_graphml(self):
+        from xml.etree.ElementTree import parse
+
+        G = self.attribute_named_key_ids_graph
+        fh = io.BytesIO()
+        self.writer(G, fh, named_key_ids=True)
+        fh.seek(0)
+        H = nx.read_graphml(fh)
+        fh.seek(0)
+
+        assert nodes_equal(G.nodes(), H.nodes())
+        assert edges_equal(G.edges(), H.edges())
+        assert edges_equal(G.edges(data=True), H.edges(data=True))
+        self.attribute_named_key_ids_fh.seek(0)
+
+        xml = parse(fh)
+        # Children are the key elements, and the graph element
+        children = list(xml.getroot())
+        assert len(children) == 4
+
+        keys = [child.items() for child in children[:3]]
+
+        assert len(keys) == 3
+        assert ("id", "edge_prop") in keys[0]
+        assert ("attr.name", "edge_prop") in keys[0]
+        assert ("id", "prop2") in keys[1]
+        assert ("attr.name", "prop2") in keys[1]
+        assert ("id", "prop1") in keys[2]
+        assert ("attr.name", "prop1") in keys[2]
+
+        # Confirm the read graph nodes/edge are identical when compared to
+        # default writing behavior.
+        default_behavior_fh = io.BytesIO()
+        nx.write_graphml(G, default_behavior_fh)
+        default_behavior_fh.seek(0)
+        H = nx.read_graphml(default_behavior_fh)
+
+        named_key_ids_behavior_fh = io.BytesIO()
+        nx.write_graphml(G, named_key_ids_behavior_fh, named_key_ids=True)
+        named_key_ids_behavior_fh.seek(0)
+        J = nx.read_graphml(named_key_ids_behavior_fh)
+
+        assert all(n1 == n2 for (n1, n2) in zip(H.nodes, J.nodes))
+        assert all(e1 == e2 for (e1, e2) in zip(H.edges, J.edges))
+
+    def test_write_read_attribute_numeric_type_graphml(self):
+        from xml.etree.ElementTree import parse
+
+        G = self.attribute_numeric_type_graph
+        fh = io.BytesIO()
+        self.writer(G, fh, infer_numeric_types=True)
+        fh.seek(0)
+        H = nx.read_graphml(fh)
+        fh.seek(0)
+
+        assert nodes_equal(G.nodes(), H.nodes())
+        assert edges_equal(G.edges(), H.edges())
+        assert edges_equal(G.edges(data=True), H.edges(data=True))
+        self.attribute_numeric_type_fh.seek(0)
+
+        xml = parse(fh)
+        # Children are the key elements, and the graph element
+        children = list(xml.getroot())
+        assert len(children) == 3
+
+        keys = [child.items() for child in children[:2]]
+
+        assert len(keys) == 2
+        assert ("attr.type", "double") in keys[0]
+        assert ("attr.type", "double") in keys[1]
+
+    def test_more_multigraph_keys(self, tmp_path):
+        """Writing keys as edge id attributes means keys become strings.
+        The original keys are stored as data, so read them back in
+        if `str(key) == edge_id`
+        This allows the adjacency to remain the same.
+        """
+        G = nx.MultiGraph()
+        G.add_edges_from([("a", "b", 2), ("a", "b", 3)])
+        fname = tmp_path / "test.graphml"
+        self.writer(G, fname)
+        H = nx.read_graphml(fname)
+        assert H.is_multigraph()
+        assert edges_equal(G.edges(keys=True), H.edges(keys=True))
+        assert G._adj == H._adj
+
+    def test_default_attribute(self):
+        G = nx.Graph(name="Fred")
+        G.add_node(1, label=1, color="green")
+        nx.add_path(G, [0, 1, 2, 3])
+        G.add_edge(1, 2, weight=3)
+        G.graph["node_default"] = {"color": "yellow"}
+        G.graph["edge_default"] = {"weight": 7}
+        fh = io.BytesIO()
+        self.writer(G, fh)
+        fh.seek(0)
+        H = nx.read_graphml(fh, node_type=int)
+        assert nodes_equal(G.nodes(), H.nodes())
+        assert edges_equal(G.edges(), H.edges())
+        assert G.graph == H.graph
+
+    def test_mixed_type_attributes(self):
+        G = nx.MultiGraph()
+        G.add_node("n0", special=False)
+        G.add_node("n1", special=0)
+        G.add_edge("n0", "n1", special=False)
+        G.add_edge("n0", "n1", special=0)
+        fh = io.BytesIO()
+        self.writer(G, fh)
+        fh.seek(0)
+        H = nx.read_graphml(fh)
+        assert not H.nodes["n0"]["special"]
+        assert H.nodes["n1"]["special"] == 0
+        assert not H.edges["n0", "n1", 0]["special"]
+        assert H.edges["n0", "n1", 1]["special"] == 0
+
+    def test_str_number_mixed_type_attributes(self):
+        G = nx.MultiGraph()
+        G.add_node("n0", special="hello")
+        G.add_node("n1", special=0)
+        G.add_edge("n0", "n1", special="hello")
+        G.add_edge("n0", "n1", special=0)
+        fh = io.BytesIO()
+        self.writer(G, fh)
+        fh.seek(0)
+        H = nx.read_graphml(fh)
+        assert H.nodes["n0"]["special"] == "hello"
+        assert H.nodes["n1"]["special"] == 0
+        assert H.edges["n0", "n1", 0]["special"] == "hello"
+        assert H.edges["n0", "n1", 1]["special"] == 0
+
+    def test_mixed_int_type_number_attributes(self):
+        np = pytest.importorskip("numpy")
+        G = nx.MultiGraph()
+        G.add_node("n0", special=np.int64(0))
+        G.add_node("n1", special=1)
+        G.add_edge("n0", "n1", special=np.int64(2))
+        G.add_edge("n0", "n1", special=3)
+        fh = io.BytesIO()
+        self.writer(G, fh)
+        fh.seek(0)
+        H = nx.read_graphml(fh)
+        assert H.nodes["n0"]["special"] == 0
+        assert H.nodes["n1"]["special"] == 1
+        assert H.edges["n0", "n1", 0]["special"] == 2
+        assert H.edges["n0", "n1", 1]["special"] == 3
+
+    def test_multigraph_to_graph(self, tmp_path):
+        # test converting multigraph to graph if no parallel edges found
+        G = nx.MultiGraph()
+        G.add_edges_from([("a", "b", 2), ("b", "c", 3)])  # no multiedges
+        fname = tmp_path / "test.graphml"
+        self.writer(G, fname)
+        H = nx.read_graphml(fname)
+        assert not H.is_multigraph()
+        H = nx.read_graphml(fname, force_multigraph=True)
+        assert H.is_multigraph()
+
+        # add a multiedge
+        G.add_edge("a", "b", "e-id")
+        fname = tmp_path / "test.graphml"
+        self.writer(G, fname)
+        H = nx.read_graphml(fname)
+        assert H.is_multigraph()
+        H = nx.read_graphml(fname, force_multigraph=True)
+        assert H.is_multigraph()
+
+    def test_write_generate_edge_id_from_attribute(self, tmp_path):
+        from xml.etree.ElementTree import parse
+
+        G = nx.Graph()
+        G.add_edges_from([("a", "b"), ("b", "c"), ("a", "c")])
+        edge_attributes = {e: str(e) for e in G.edges}
+        nx.set_edge_attributes(G, edge_attributes, "eid")
+        fname = tmp_path / "test.graphml"
+        # set edge_id_from_attribute e.g. "eid" for write_graphml()
+        self.writer(G, fname, edge_id_from_attribute="eid")
+        # set edge_id_from_attribute e.g. "eid" for generate_graphml()
+        generator = nx.generate_graphml(G, edge_id_from_attribute="eid")
+
+        H = nx.read_graphml(fname)
+        assert nodes_equal(G.nodes(), H.nodes())
+        assert edges_equal(G.edges(), H.edges())
+        # NetworkX adds explicit edge "id" from file as attribute
+        nx.set_edge_attributes(G, edge_attributes, "id")
+        assert edges_equal(G.edges(data=True), H.edges(data=True))
+
+        tree = parse(fname)
+        children = list(tree.getroot())
+        assert len(children) == 2
+        edge_ids = [
+            edge.attrib["id"]
+            for edge in tree.getroot().findall(
+                ".//{http://graphml.graphdrawing.org/xmlns}edge"
+            )
+        ]
+        # verify edge id value is equal to specified attribute value
+        assert sorted(edge_ids) == sorted(edge_attributes.values())
+
+        # check graphml generated from generate_graphml()
+        data = "".join(generator)
+        J = nx.parse_graphml(data)
+        assert sorted(G.nodes()) == sorted(J.nodes())
+        assert sorted(G.edges()) == sorted(J.edges())
+        # NetworkX adds explicit edge "id" from file as attribute
+        nx.set_edge_attributes(G, edge_attributes, "id")
+        assert edges_equal(G.edges(data=True), J.edges(data=True))
+
+    def test_multigraph_write_generate_edge_id_from_attribute(self, tmp_path):
+        from xml.etree.ElementTree import parse
+
+        G = nx.MultiGraph()
+        G.add_edges_from([("a", "b"), ("b", "c"), ("a", "c"), ("a", "b")])
+        edge_attributes = {e: str(e) for e in G.edges}
+        nx.set_edge_attributes(G, edge_attributes, "eid")
+        fname = tmp_path / "test.graphml"
+        # set edge_id_from_attribute e.g. "eid" for write_graphml()
+        self.writer(G, fname, edge_id_from_attribute="eid")
+        # set edge_id_from_attribute e.g. "eid" for generate_graphml()
+        generator = nx.generate_graphml(G, edge_id_from_attribute="eid")
+
+        H = nx.read_graphml(fname)
+        assert H.is_multigraph()
+        H = nx.read_graphml(fname, force_multigraph=True)
+        assert H.is_multigraph()
+
+        assert nodes_equal(G.nodes(), H.nodes())
+        assert edges_equal(G.edges(), H.edges())
+        assert sorted(data.get("eid") for u, v, data in H.edges(data=True)) == sorted(
+            edge_attributes.values()
+        )
+        # NetworkX uses edge_ids as keys in multigraphs if no key
+        assert sorted(key for u, v, key in H.edges(keys=True)) == sorted(
+            edge_attributes.values()
+        )
+
+        tree = parse(fname)
+        children = list(tree.getroot())
+        assert len(children) == 2
+        edge_ids = [
+            edge.attrib["id"]
+            for edge in tree.getroot().findall(
+                ".//{http://graphml.graphdrawing.org/xmlns}edge"
+            )
+        ]
+        # verify edge id value is equal to specified attribute value
+        assert sorted(edge_ids) == sorted(edge_attributes.values())
+
+        # check graphml generated from generate_graphml()
+        graphml_data = "".join(generator)
+        J = nx.parse_graphml(graphml_data)
+        assert J.is_multigraph()
+
+        assert nodes_equal(G.nodes(), J.nodes())
+        assert edges_equal(G.edges(), J.edges())
+        assert sorted(data.get("eid") for u, v, data in J.edges(data=True)) == sorted(
+            edge_attributes.values()
+        )
+        # NetworkX uses edge_ids as keys in multigraphs if no key
+        assert sorted(key for u, v, key in J.edges(keys=True)) == sorted(
+            edge_attributes.values()
+        )
+
+    def test_numpy_float64(self, tmp_path):
+        np = pytest.importorskip("numpy")
+        wt = np.float64(3.4)
+        G = nx.Graph([(1, 2, {"weight": wt})])
+        fname = tmp_path / "test.graphml"
+        self.writer(G, fname)
+        H = nx.read_graphml(fname, node_type=int)
+        assert G.edges == H.edges
+        wtG = G[1][2]["weight"]
+        wtH = H[1][2]["weight"]
+        assert wtG == pytest.approx(wtH, abs=1e-6)
+        assert type(wtG) == np.float64
+        assert type(wtH) == float
+
+    def test_numpy_float32(self, tmp_path):
+        np = pytest.importorskip("numpy")
+        wt = np.float32(3.4)
+        G = nx.Graph([(1, 2, {"weight": wt})])
+        fname = tmp_path / "test.graphml"
+        self.writer(G, fname)
+        H = nx.read_graphml(fname, node_type=int)
+        assert G.edges == H.edges
+        wtG = G[1][2]["weight"]
+        wtH = H[1][2]["weight"]
+        assert wtG == pytest.approx(wtH, abs=1e-6)
+        assert type(wtG) == np.float32
+        assert type(wtH) == float
+
+    def test_numpy_float64_inference(self, tmp_path):
+        np = pytest.importorskip("numpy")
+        G = self.attribute_numeric_type_graph
+        G.edges[("n1", "n1")]["weight"] = np.float64(1.1)
+        fname = tmp_path / "test.graphml"
+        self.writer(G, fname, infer_numeric_types=True)
+        H = nx.read_graphml(fname)
+        assert G._adj == H._adj
+
+    def test_unicode_attributes(self, tmp_path):
+        G = nx.Graph()
+        name1 = chr(2344) + chr(123) + chr(6543)
+        name2 = chr(5543) + chr(1543) + chr(324)
+        node_type = str
+        G.add_edge(name1, "Radiohead", foo=name2)
+        fname = tmp_path / "test.graphml"
+        self.writer(G, fname)
+        H = nx.read_graphml(fname, node_type=node_type)
+        assert G._adj == H._adj
+
+    def test_unicode_escape(self):
+        # test for handling json escaped strings in python 2 Issue #1880
+        import json
+
+        a = {"a": '{"a": "123"}'}  # an object with many chars to escape
+        sa = json.dumps(a)
+        G = nx.Graph()
+        G.graph["test"] = sa
+        fh = io.BytesIO()
+        self.writer(G, fh)
+        fh.seek(0)
+        H = nx.read_graphml(fh)
+        assert G.graph["test"] == H.graph["test"]
+
+
+class TestXMLGraphML(TestWriteGraphML):
+    writer = staticmethod(nx.write_graphml_xml)
+
+    @classmethod
+    def setup_class(cls):
+        TestWriteGraphML.setup_class()
+
+
+def test_exception_for_unsupported_datatype_node_attr():
+    """Test that a detailed exception is raised when an attribute is of a type
+    not supported by GraphML, e.g. a list"""
+    pytest.importorskip("lxml.etree")
+    # node attribute
+    G = nx.Graph()
+    G.add_node(0, my_list_attribute=[0, 1, 2])
+    fh = io.BytesIO()
+    with pytest.raises(TypeError, match="GraphML does not support"):
+        nx.write_graphml(G, fh)
+
+
+def test_exception_for_unsupported_datatype_edge_attr():
+    """Test that a detailed exception is raised when an attribute is of a type
+    not supported by GraphML, e.g. a list"""
+    pytest.importorskip("lxml.etree")
+    # edge attribute
+    G = nx.Graph()
+    G.add_edge(0, 1, my_list_attribute=[0, 1, 2])
+    fh = io.BytesIO()
+    with pytest.raises(TypeError, match="GraphML does not support"):
+        nx.write_graphml(G, fh)
+
+
+def test_exception_for_unsupported_datatype_graph_attr():
+    """Test that a detailed exception is raised when an attribute is of a type
+    not supported by GraphML, e.g. a list"""
+    pytest.importorskip("lxml.etree")
+    # graph attribute
+    G = nx.Graph()
+    G.graph["my_list_attribute"] = [0, 1, 2]
+    fh = io.BytesIO()
+    with pytest.raises(TypeError, match="GraphML does not support"):
+        nx.write_graphml(G, fh)
+
+
+def test_empty_attribute():
+    """Tests that a GraphML string with an empty attribute can be parsed
+    correctly."""
+    s = """<?xml version='1.0' encoding='utf-8'?>
+    <graphml>
+      <key id="d1" for="node" attr.name="foo" attr.type="string"/>
+      <key id="d2" for="node" attr.name="bar" attr.type="string"/>
+      <graph>
+        <node id="0">
+          <data key="d1">aaa</data>
+          <data key="d2">bbb</data>
+        </node>
+        <node id="1">
+          <data key="d1">ccc</data>
+          <data key="d2"></data>
+        </node>
+      </graph>
+    </graphml>"""
+    fh = io.BytesIO(s.encode("UTF-8"))
+    G = nx.read_graphml(fh)
+    assert G.nodes["0"] == {"foo": "aaa", "bar": "bbb"}
+    assert G.nodes["1"] == {"foo": "ccc", "bar": ""}
diff --git a/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_leda.py b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_leda.py
new file mode 100644
index 00000000..8ac5ecc3
--- /dev/null
+++ b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_leda.py
@@ -0,0 +1,30 @@
+import io
+
+import networkx as nx
+
+
+class TestLEDA:
+    def test_parse_leda(self):
+        data = """#header section         \nLEDA.GRAPH \nstring\nint\n-1\n#nodes section\n5 \n|{v1}| \n|{v2}| \n|{v3}| \n|{v4}| \n|{v5}| \n\n#edges section\n7 \n1 2 0 |{4}| \n1 3 0 |{3}| \n2 3 0 |{2}| \n3 4 0 |{3}| \n3 5 0 |{7}| \n4 5 0 |{6}| \n5 1 0 |{foo}|"""
+        G = nx.parse_leda(data)
+        G = nx.parse_leda(data.split("\n"))
+        assert sorted(G.nodes()) == ["v1", "v2", "v3", "v4", "v5"]
+        assert sorted(G.edges(data=True)) == [
+            ("v1", "v2", {"label": "4"}),
+            ("v1", "v3", {"label": "3"}),
+            ("v2", "v3", {"label": "2"}),
+            ("v3", "v4", {"label": "3"}),
+            ("v3", "v5", {"label": "7"}),
+            ("v4", "v5", {"label": "6"}),
+            ("v5", "v1", {"label": "foo"}),
+        ]
+
+    def test_read_LEDA(self):
+        fh = io.BytesIO()
+        data = """#header section         \nLEDA.GRAPH \nstring\nint\n-1\n#nodes section\n5 \n|{v1}| \n|{v2}| \n|{v3}| \n|{v4}| \n|{v5}| \n\n#edges section\n7 \n1 2 0 |{4}| \n1 3 0 |{3}| \n2 3 0 |{2}| \n3 4 0 |{3}| \n3 5 0 |{7}| \n4 5 0 |{6}| \n5 1 0 |{foo}|"""
+        G = nx.parse_leda(data)
+        fh.write(data.encode("UTF-8"))
+        fh.seek(0)
+        Gin = nx.read_leda(fh)
+        assert sorted(G.nodes()) == sorted(Gin.nodes())
+        assert sorted(G.edges()) == sorted(Gin.edges())
diff --git a/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_p2g.py b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_p2g.py
new file mode 100644
index 00000000..e4c50de7
--- /dev/null
+++ b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_p2g.py
@@ -0,0 +1,62 @@
+import io
+
+import networkx as nx
+from networkx.readwrite.p2g import read_p2g, write_p2g
+from networkx.utils import edges_equal
+
+
+class TestP2G:
+    @classmethod
+    def setup_class(cls):
+        cls.G = nx.Graph(name="test")
+        e = [("a", "b"), ("b", "c"), ("c", "d"), ("d", "e"), ("e", "f"), ("a", "f")]
+        cls.G.add_edges_from(e)
+        cls.G.add_node("g")
+        cls.DG = nx.DiGraph(cls.G)
+
+    def test_read_p2g(self):
+        s = b"""\
+name
+3 4
+a
+1 2
+b
+
+c
+0 2
+"""
+        bytesIO = io.BytesIO(s)
+        G = read_p2g(bytesIO)
+        assert G.name == "name"
+        assert sorted(G) == ["a", "b", "c"]
+        edges = [(str(u), str(v)) for u, v in G.edges()]
+        assert edges_equal(G.edges(), [("a", "c"), ("a", "b"), ("c", "a"), ("c", "c")])
+
+    def test_write_p2g(self):
+        s = b"""foo
+3 2
+1
+1 
+2
+2 
+3
+
+"""
+        fh = io.BytesIO()
+        G = nx.DiGraph()
+        G.name = "foo"
+        G.add_edges_from([(1, 2), (2, 3)])
+        write_p2g(G, fh)
+        fh.seek(0)
+        r = fh.read()
+        assert r == s
+
+    def test_write_read_p2g(self):
+        fh = io.BytesIO()
+        G = nx.DiGraph()
+        G.name = "foo"
+        G.add_edges_from([("a", "b"), ("b", "c")])
+        write_p2g(G, fh)
+        fh.seek(0)
+        H = read_p2g(fh)
+        assert edges_equal(G.edges(), H.edges())
diff --git a/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_pajek.py b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_pajek.py
new file mode 100644
index 00000000..317ebe8e
--- /dev/null
+++ b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_pajek.py
@@ -0,0 +1,126 @@
+"""
+Pajek tests
+"""
+
+import networkx as nx
+from networkx.utils import edges_equal, nodes_equal
+
+
+class TestPajek:
+    @classmethod
+    def setup_class(cls):
+        cls.data = """*network Tralala\n*vertices 4\n   1 "A1"         0.0938 0.0896   ellipse x_fact 1 y_fact 1\n   2 "Bb"         0.8188 0.2458   ellipse x_fact 1 y_fact 1\n   3 "C"          0.3688 0.7792   ellipse x_fact 1\n   4 "D2"         0.9583 0.8563   ellipse x_fact 1\n*arcs\n1 1 1  h2 0 w 3 c Blue s 3 a1 -130 k1 0.6 a2 -130 k2 0.6 ap 0.5 l "Bezier loop" lc BlueViolet fos 20 lr 58 lp 0.3 la 360\n2 1 1  h2 0 a1 120 k1 1.3 a2 -120 k2 0.3 ap 25 l "Bezier arc" lphi 270 la 180 lr 19 lp 0.5\n1 2 1  h2 0 a1 40 k1 2.8 a2 30 k2 0.8 ap 25 l "Bezier arc" lphi 90 la 0 lp 0.65\n4 2 -1  h2 0 w 1 k1 -2 k2 250 ap 25 l "Circular arc" c Red lc OrangeRed\n3 4 1  p Dashed h2 0 w 2 c OliveGreen ap 25 l "Straight arc" lc PineGreen\n1 3 1  p Dashed h2 0 w 5 k1 -1 k2 -20 ap 25 l "Oval arc" c Brown lc Black\n3 3 -1  h1 6 w 1 h2 12 k1 -2 k2 -15 ap 0.5 l "Circular loop" c Red lc OrangeRed lphi 270 la 180"""
+        cls.G = nx.MultiDiGraph()
+        cls.G.add_nodes_from(["A1", "Bb", "C", "D2"])
+        cls.G.add_edges_from(
+            [
+                ("A1", "A1"),
+                ("A1", "Bb"),
+                ("A1", "C"),
+                ("Bb", "A1"),
+                ("C", "C"),
+                ("C", "D2"),
+                ("D2", "Bb"),
+            ]
+        )
+
+        cls.G.graph["name"] = "Tralala"
+
+    def test_parse_pajek_simple(self):
+        # Example without node positions or shape
+        data = """*Vertices 2\n1 "1"\n2 "2"\n*Edges\n1 2\n2 1"""
+        G = nx.parse_pajek(data)
+        assert sorted(G.nodes()) == ["1", "2"]
+        assert edges_equal(G.edges(), [("1", "2"), ("1", "2")])
+
+    def test_parse_pajek(self):
+        G = nx.parse_pajek(self.data)
+        assert sorted(G.nodes()) == ["A1", "Bb", "C", "D2"]
+        assert edges_equal(
+            G.edges(),
+            [
+                ("A1", "A1"),
+                ("A1", "Bb"),
+                ("A1", "C"),
+                ("Bb", "A1"),
+                ("C", "C"),
+                ("C", "D2"),
+                ("D2", "Bb"),
+            ],
+        )
+
+    def test_parse_pajet_mat(self):
+        data = """*Vertices 3\n1 "one"\n2 "two"\n3 "three"\n*Matrix\n1 1 0\n0 1 0\n0 1 0\n"""
+        G = nx.parse_pajek(data)
+        assert set(G.nodes()) == {"one", "two", "three"}
+        assert G.nodes["two"] == {"id": "2"}
+        assert edges_equal(
+            set(G.edges()),
+            {("one", "one"), ("two", "one"), ("two", "two"), ("two", "three")},
+        )
+
+    def test_read_pajek(self, tmp_path):
+        G = nx.parse_pajek(self.data)
+        # Read data from file
+        fname = tmp_path / "test.pjk"
+        with open(fname, "wb") as fh:
+            fh.write(self.data.encode("UTF-8"))
+
+        Gin = nx.read_pajek(fname)
+        assert sorted(G.nodes()) == sorted(Gin.nodes())
+        assert edges_equal(G.edges(), Gin.edges())
+        assert self.G.graph == Gin.graph
+        for n in G:
+            assert G.nodes[n] == Gin.nodes[n]
+
+    def test_write_pajek(self):
+        import io
+
+        G = nx.parse_pajek(self.data)
+        fh = io.BytesIO()
+        nx.write_pajek(G, fh)
+        fh.seek(0)
+        H = nx.read_pajek(fh)
+        assert nodes_equal(list(G), list(H))
+        assert edges_equal(list(G.edges()), list(H.edges()))
+        # Graph name is left out for now, therefore it is not tested.
+        # assert_equal(G.graph, H.graph)
+
+    def test_ignored_attribute(self):
+        import io
+
+        G = nx.Graph()
+        fh = io.BytesIO()
+        G.add_node(1, int_attr=1)
+        G.add_node(2, empty_attr="  ")
+        G.add_edge(1, 2, int_attr=2)
+        G.add_edge(2, 3, empty_attr="  ")
+
+        import warnings
+
+        with warnings.catch_warnings(record=True) as w:
+            nx.write_pajek(G, fh)
+            assert len(w) == 4
+
+    def test_noname(self):
+        # Make sure we can parse a line such as:  *network
+        # Issue #952
+        line = "*network\n"
+        other_lines = self.data.split("\n")[1:]
+        data = line + "\n".join(other_lines)
+        G = nx.parse_pajek(data)
+
+    def test_unicode(self):
+        import io
+
+        G = nx.Graph()
+        name1 = chr(2344) + chr(123) + chr(6543)
+        name2 = chr(5543) + chr(1543) + chr(324)
+        G.add_edge(name1, "Radiohead", foo=name2)
+        fh = io.BytesIO()
+        nx.write_pajek(G, fh)
+        fh.seek(0)
+        H = nx.read_pajek(fh)
+        assert nodes_equal(list(G), list(H))
+        assert edges_equal(list(G.edges()), list(H.edges()))
+        assert G.graph == H.graph
diff --git a/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_sparse6.py b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_sparse6.py
new file mode 100644
index 00000000..344ad0e4
--- /dev/null
+++ b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_sparse6.py
@@ -0,0 +1,166 @@
+from io import BytesIO
+
+import pytest
+
+import networkx as nx
+from networkx.utils import edges_equal, nodes_equal
+
+
+class TestSparseGraph6:
+    def test_from_sparse6_bytes(self):
+        data = b":Q___eDcdFcDeFcE`GaJ`IaHbKNbLM"
+        G = nx.from_sparse6_bytes(data)
+        assert nodes_equal(
+            sorted(G.nodes()),
+            [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17],
+        )
+        assert edges_equal(
+            G.edges(),
+            [
+                (0, 1),
+                (0, 2),
+                (0, 3),
+                (1, 12),
+                (1, 14),
+                (2, 13),
+                (2, 15),
+                (3, 16),
+                (3, 17),
+                (4, 7),
+                (4, 9),
+                (4, 11),
+                (5, 6),
+                (5, 8),
+                (5, 9),
+                (6, 10),
+                (6, 11),
+                (7, 8),
+                (7, 10),
+                (8, 12),
+                (9, 15),
+                (10, 14),
+                (11, 13),
+                (12, 16),
+                (13, 17),
+                (14, 17),
+                (15, 16),
+            ],
+        )
+
+    def test_from_bytes_multigraph_graph(self):
+        graph_data = b":An"
+        G = nx.from_sparse6_bytes(graph_data)
+        assert type(G) == nx.Graph
+        multigraph_data = b":Ab"
+        M = nx.from_sparse6_bytes(multigraph_data)
+        assert type(M) == nx.MultiGraph
+
+    def test_read_sparse6(self):
+        data = b":Q___eDcdFcDeFcE`GaJ`IaHbKNbLM"
+        G = nx.from_sparse6_bytes(data)
+        fh = BytesIO(data)
+        Gin = nx.read_sparse6(fh)
+        assert nodes_equal(G.nodes(), Gin.nodes())
+        assert edges_equal(G.edges(), Gin.edges())
+
+    def test_read_many_graph6(self):
+        # Read many graphs into list
+        data = b":Q___eDcdFcDeFcE`GaJ`IaHbKNbLM\n" b":Q___dCfDEdcEgcbEGbFIaJ`JaHN`IM"
+        fh = BytesIO(data)
+        glist = nx.read_sparse6(fh)
+        assert len(glist) == 2
+        for G in glist:
+            assert nodes_equal(
+                G.nodes(),
+                [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17],
+            )
+
+
+class TestWriteSparse6:
+    """Unit tests for writing graphs in the sparse6 format.
+
+    Most of the test cases were checked against the sparse6 encoder in Sage.
+
+    """
+
+    def test_null_graph(self):
+        G = nx.null_graph()
+        result = BytesIO()
+        nx.write_sparse6(G, result)
+        assert result.getvalue() == b">>sparse6<<:?\n"
+
+    def test_trivial_graph(self):
+        G = nx.trivial_graph()
+        result = BytesIO()
+        nx.write_sparse6(G, result)
+        assert result.getvalue() == b">>sparse6<<:@\n"
+
+    def test_empty_graph(self):
+        G = nx.empty_graph(5)
+        result = BytesIO()
+        nx.write_sparse6(G, result)
+        assert result.getvalue() == b">>sparse6<<:D\n"
+
+    def test_large_empty_graph(self):
+        G = nx.empty_graph(68)
+        result = BytesIO()
+        nx.write_sparse6(G, result)
+        assert result.getvalue() == b">>sparse6<<:~?@C\n"
+
+    def test_very_large_empty_graph(self):
+        G = nx.empty_graph(258049)
+        result = BytesIO()
+        nx.write_sparse6(G, result)
+        assert result.getvalue() == b">>sparse6<<:~~???~?@\n"
+
+    def test_complete_graph(self):
+        G = nx.complete_graph(4)
+        result = BytesIO()
+        nx.write_sparse6(G, result)
+        assert result.getvalue() == b">>sparse6<<:CcKI\n"
+
+    def test_no_header(self):
+        G = nx.complete_graph(4)
+        result = BytesIO()
+        nx.write_sparse6(G, result, header=False)
+        assert result.getvalue() == b":CcKI\n"
+
+    def test_padding(self):
+        codes = (b":Cdv", b":DaYn", b":EaYnN", b":FaYnL", b":GaYnLz")
+        for n, code in enumerate(codes, start=4):
+            G = nx.path_graph(n)
+            result = BytesIO()
+            nx.write_sparse6(G, result, header=False)
+            assert result.getvalue() == code + b"\n"
+
+    def test_complete_bipartite(self):
+        G = nx.complete_bipartite_graph(6, 9)
+        result = BytesIO()
+        nx.write_sparse6(G, result)
+        # Compared with sage
+        expected = b">>sparse6<<:Nk" + b"?G`cJ" * 9 + b"\n"
+        assert result.getvalue() == expected
+
+    def test_read_write_inverse(self):
+        for i in list(range(13)) + [31, 47, 62, 63, 64, 72]:
+            m = min(2 * i, i * i // 2)
+            g = nx.random_graphs.gnm_random_graph(i, m, seed=i)
+            gstr = BytesIO()
+            nx.write_sparse6(g, gstr, header=False)
+            # Strip the trailing newline.
+            gstr = gstr.getvalue().rstrip()
+            g2 = nx.from_sparse6_bytes(gstr)
+            assert g2.order() == g.order()
+            assert edges_equal(g2.edges(), g.edges())
+
+    def test_no_directed_graphs(self):
+        with pytest.raises(nx.NetworkXNotImplemented):
+            nx.write_sparse6(nx.DiGraph(), BytesIO())
+
+    def test_write_path(self, tmp_path):
+        # Get a valid temporary file name
+        fullfilename = str(tmp_path / "test.s6")
+        # file should be closed now, so write_sparse6 can open it
+        nx.write_sparse6(nx.null_graph(), fullfilename)
+        with open(fullfilename, mode="rb") as fh:
+            assert fh.read() == b">>sparse6<<:?\n"
diff --git a/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_text.py b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_text.py
new file mode 100644
index 00000000..b2b74482
--- /dev/null
+++ b/.venv/lib/python3.12/site-packages/networkx/readwrite/tests/test_text.py
@@ -0,0 +1,1742 @@
+import random
+from itertools import product
+from textwrap import dedent
+
+import pytest
+
+import networkx as nx
+
+
+def test_generate_network_text_forest_directed():
+    # Create a directed forest with labels
+    graph = nx.balanced_tree(r=2, h=2, create_using=nx.DiGraph)
+    for node in graph.nodes:
+        graph.nodes[node]["label"] = "node_" + chr(ord("a") + node)
+
+    node_target = dedent(
+        """
+        ╙── 0
+            ├─╼ 1
+            │   ├─╼ 3
+            │   └─╼ 4
+            └─╼ 2
+                ├─╼ 5
+                └─╼ 6
+        """
+    ).strip()
+
+    label_target = dedent(
+        """
+        ╙── node_a
+            ├─╼ node_b
+            │   ├─╼ node_d
+            │   └─╼ node_e
+            └─╼ node_c
+                ├─╼ node_f
+                └─╼ node_g
+        """
+    ).strip()
+
+    # Basic node case
+    ret = nx.generate_network_text(graph, with_labels=False)
+    assert "\n".join(ret) == node_target
+
+    # Basic label case
+    ret = nx.generate_network_text(graph, with_labels=True)
+    assert "\n".join(ret) == label_target
+
+
+def test_write_network_text_empty_graph():
+    def _graph_str(g, **kw):
+        printbuf = []
+        nx.write_network_text(g, printbuf.append, end="", **kw)
+        return "\n".join(printbuf)
+
+    assert _graph_str(nx.DiGraph()) == "╙"
+    assert _graph_str(nx.Graph()) == "╙"
+    assert _graph_str(nx.DiGraph(), ascii_only=True) == "+"
+    assert _graph_str(nx.Graph(), ascii_only=True) == "+"
+
+
+def test_write_network_text_within_forest_glyph():
+    g = nx.DiGraph()
+    g.add_nodes_from([1, 2, 3, 4])
+    g.add_edge(2, 4)
+    lines = []
+    write = lines.append
+    nx.write_network_text(g, path=write, end="")
+    nx.write_network_text(g, path=write, ascii_only=True, end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        ╟── 1
+        ╟── 2
+        ╎   └─╼ 4
+        ╙── 3
+        +-- 1
+        +-- 2
+        :   L-> 4
+        +-- 3
+        """
+    ).strip()
+    assert text == target
+
+
+def test_generate_network_text_directed_multi_tree():
+    tree1 = nx.balanced_tree(r=2, h=2, create_using=nx.DiGraph)
+    tree2 = nx.balanced_tree(r=2, h=2, create_using=nx.DiGraph)
+    forest = nx.disjoint_union_all([tree1, tree2])
+    ret = "\n".join(nx.generate_network_text(forest))
+
+    target = dedent(
+        """
+        ╟── 0
+        ╎   ├─╼ 1
+        ╎   │   ├─╼ 3
+        ╎   │   └─╼ 4
+        ╎   └─╼ 2
+        ╎       ├─╼ 5
+        ╎       └─╼ 6
+        ╙── 7
+            ├─╼ 8
+            │   ├─╼ 10
+            │   └─╼ 11
+            └─╼ 9
+                ├─╼ 12
+                └─╼ 13
+        """
+    ).strip()
+    assert ret == target
+
+    tree3 = nx.balanced_tree(r=2, h=2, create_using=nx.DiGraph)
+    forest = nx.disjoint_union_all([tree1, tree2, tree3])
+    ret = "\n".join(nx.generate_network_text(forest, sources=[0, 14, 7]))
+
+    target = dedent(
+        """
+        ╟── 0
+        ╎   ├─╼ 1
+        ╎   │   ├─╼ 3
+        ╎   │   └─╼ 4
+        ╎   └─╼ 2
+        ╎       ├─╼ 5
+        ╎       └─╼ 6
+        ╟── 14
+        ╎   ├─╼ 15
+        ╎   │   ├─╼ 17
+        ╎   │   └─╼ 18
+        ╎   └─╼ 16
+        ╎       ├─╼ 19
+        ╎       └─╼ 20
+        ╙── 7
+            ├─╼ 8
+            │   ├─╼ 10
+            │   └─╼ 11
+            └─╼ 9
+                ├─╼ 12
+                └─╼ 13
+        """
+    ).strip()
+    assert ret == target
+
+    ret = "\n".join(
+        nx.generate_network_text(forest, sources=[0, 14, 7], ascii_only=True)
+    )
+
+    target = dedent(
+        """
+        +-- 0
+        :   |-> 1
+        :   |   |-> 3
+        :   |   L-> 4
+        :   L-> 2
+        :       |-> 5
+        :       L-> 6
+        +-- 14
+        :   |-> 15
+        :   |   |-> 17
+        :   |   L-> 18
+        :   L-> 16
+        :       |-> 19
+        :       L-> 20
+        +-- 7
+            |-> 8
+            |   |-> 10
+            |   L-> 11
+            L-> 9
+                |-> 12
+                L-> 13
+        """
+    ).strip()
+    assert ret == target
+
+
+def test_generate_network_text_undirected_multi_tree():
+    tree1 = nx.balanced_tree(r=2, h=2, create_using=nx.Graph)
+    tree2 = nx.balanced_tree(r=2, h=2, create_using=nx.Graph)
+    tree2 = nx.relabel_nodes(tree2, {n: n + len(tree1) for n in tree2.nodes})
+    forest = nx.union(tree1, tree2)
+    ret = "\n".join(nx.generate_network_text(forest, sources=[0, 7]))
+
+    target = dedent(
+        """
+        ╟── 0
+        ╎   ├── 1
+        ╎   │   ├── 3
+        ╎   │   └── 4
+        ╎   └── 2
+        ╎       ├── 5
+        ╎       └── 6
+        ╙── 7
+            ├── 8
+            │   ├── 10
+            │   └── 11
+            └── 9
+                ├── 12
+                └── 13
+        """
+    ).strip()
+    assert ret == target
+
+    ret = "\n".join(nx.generate_network_text(forest, sources=[0, 7], ascii_only=True))
+
+    target = dedent(
+        """
+        +-- 0
+        :   |-- 1
+        :   |   |-- 3
+        :   |   L-- 4
+        :   L-- 2
+        :       |-- 5
+        :       L-- 6
+        +-- 7
+            |-- 8
+            |   |-- 10
+            |   L-- 11
+            L-- 9
+                |-- 12
+                L-- 13
+        """
+    ).strip()
+    assert ret == target
+
+
+def test_generate_network_text_forest_undirected():
+    # Create a directed forest
+    graph = nx.balanced_tree(r=2, h=2, create_using=nx.Graph)
+
+    node_target0 = dedent(
+        """
+        ╙── 0
+            ├── 1
+            │   ├── 3
+            │   └── 4
+            └── 2
+                ├── 5
+                └── 6
+        """
+    ).strip()
+
+    # defined starting point
+    ret = "\n".join(nx.generate_network_text(graph, sources=[0]))
+    assert ret == node_target0
+
+    # defined starting point
+    node_target2 = dedent(
+        """
+        ╙── 2
+            ├── 0
+            │   └── 1
+            │       ├── 3
+            │       └── 4
+            ├── 5
+            └── 6
+        """
+    ).strip()
+    ret = "\n".join(nx.generate_network_text(graph, sources=[2]))
+    assert ret == node_target2
+
+
+def test_generate_network_text_overspecified_sources():
+    """
+    When sources are directly specified, we won't be able to determine when we
+    are in the last component, so there will always be a trailing, leftmost
+    pipe.
+    """
+    graph = nx.disjoint_union_all(
+        [
+            nx.balanced_tree(r=2, h=1, create_using=nx.DiGraph),
+            nx.balanced_tree(r=1, h=2, create_using=nx.DiGraph),
+            nx.balanced_tree(r=2, h=1, create_using=nx.DiGraph),
+        ]
+    )
+
+    # defined starting point
+    target1 = dedent(
+        """
+        ╟── 0
+        ╎   ├─╼ 1
+        ╎   └─╼ 2
+        ╟── 3
+        ╎   └─╼ 4
+        ╎       └─╼ 5
+        ╟── 6
+        ╎   ├─╼ 7
+        ╎   └─╼ 8
+        """
+    ).strip()
+
+    target2 = dedent(
+        """
+        ╟── 0
+        ╎   ├─╼ 1
+        ╎   └─╼ 2
+        ╟── 3
+        ╎   └─╼ 4
+        ╎       └─╼ 5
+        ╙── 6
+            ├─╼ 7
+            └─╼ 8
+        """
+    ).strip()
+
+    got1 = "\n".join(nx.generate_network_text(graph, sources=graph.nodes))
+    got2 = "\n".join(nx.generate_network_text(graph))
+    assert got1 == target1
+    assert got2 == target2
+
+
+def test_write_network_text_iterative_add_directed_edges():
+    """
+    Walk through the cases going from a disconnected to fully connected graph
+    """
+    graph = nx.DiGraph()
+    graph.add_nodes_from([1, 2, 3, 4])
+    lines = []
+    write = lines.append
+    write("--- initial state ---")
+    nx.write_network_text(graph, path=write, end="")
+    for i, j in product(graph.nodes, graph.nodes):
+        write(f"--- add_edge({i}, {j}) ---")
+        graph.add_edge(i, j)
+        nx.write_network_text(graph, path=write, end="")
+    text = "\n".join(lines)
+    # defined starting point
+    target = dedent(
+        """
+        --- initial state ---
+        ╟── 1
+        ╟── 2
+        ╟── 3
+        ╙── 4
+        --- add_edge(1, 1) ---
+        ╟── 1 ╾ 1
+        ╎   └─╼  ...
+        ╟── 2
+        ╟── 3
+        ╙── 4
+        --- add_edge(1, 2) ---
+        ╟── 1 ╾ 1
+        ╎   ├─╼ 2
+        ╎   └─╼  ...
+        ╟── 3
+        ╙── 4
+        --- add_edge(1, 3) ---
+        ╟── 1 ╾ 1
+        ╎   ├─╼ 2
+        ╎   ├─╼ 3
+        ╎   └─╼  ...
+        ╙── 4
+        --- add_edge(1, 4) ---
+        ╙── 1 ╾ 1
+            ├─╼ 2
+            ├─╼ 3
+            ├─╼ 4
+            └─╼  ...
+        --- add_edge(2, 1) ---
+        ╙── 2 ╾ 1
+            └─╼ 1 ╾ 1
+                ├─╼ 3
+                ├─╼ 4
+                └─╼  ...
+        --- add_edge(2, 2) ---
+        ╙── 1 ╾ 1, 2
+            ├─╼ 2 ╾ 2
+            │   └─╼  ...
+            ├─╼ 3
+            ├─╼ 4
+            └─╼  ...
+        --- add_edge(2, 3) ---
+        ╙── 1 ╾ 1, 2
+            ├─╼ 2 ╾ 2
+            │   ├─╼ 3 ╾ 1
+            │   └─╼  ...
+            ├─╼ 4
+            └─╼  ...
+        --- add_edge(2, 4) ---
+        ╙── 1 ╾ 1, 2
+            ├─╼ 2 ╾ 2
+            │   ├─╼ 3 ╾ 1
+            │   ├─╼ 4 ╾ 1
+            │   └─╼  ...
+            └─╼  ...
+        --- add_edge(3, 1) ---
+        ╙── 2 ╾ 1, 2
+            ├─╼ 1 ╾ 1, 3
+            │   ├─╼ 3 ╾ 2
+            │   │   └─╼  ...
+            │   ├─╼ 4 ╾ 2
+            │   └─╼  ...
+            └─╼  ...
+        --- add_edge(3, 2) ---
+        ╙── 3 ╾ 1, 2
+            ├─╼ 1 ╾ 1, 2
+            │   ├─╼ 2 ╾ 2, 3
+            │   │   ├─╼ 4 ╾ 1
+            │   │   └─╼  ...
+            │   └─╼  ...
+            └─╼  ...
+        --- add_edge(3, 3) ---
+        ╙── 1 ╾ 1, 2, 3
+            ├─╼ 2 ╾ 2, 3
+            │   ├─╼ 3 ╾ 1, 3
+            │   │   └─╼  ...
+            │   ├─╼ 4 ╾ 1
+            │   └─╼  ...
+            └─╼  ...
+        --- add_edge(3, 4) ---
+        ╙── 1 ╾ 1, 2, 3
+            ├─╼ 2 ╾ 2, 3
+            │   ├─╼ 3 ╾ 1, 3
+            │   │   ├─╼ 4 ╾ 1, 2
+            │   │   └─╼  ...
+            │   └─╼  ...
+            └─╼  ...
+        --- add_edge(4, 1) ---
+        ╙── 2 ╾ 1, 2, 3
+            ├─╼ 1 ╾ 1, 3, 4
+            │   ├─╼ 3 ╾ 2, 3
+            │   │   ├─╼ 4 ╾ 1, 2
+            │   │   │   └─╼  ...
+            │   │   └─╼  ...
+            │   └─╼  ...
+            └─╼  ...
+        --- add_edge(4, 2) ---
+        ╙── 3 ╾ 1, 2, 3
+            ├─╼ 1 ╾ 1, 2, 4
+            │   ├─╼ 2 ╾ 2, 3, 4
+            │   │   ├─╼ 4 ╾ 1, 3
+            │   │   │   └─╼  ...
+            │   │   └─╼  ...
+            │   └─╼  ...
+            └─╼  ...
+        --- add_edge(4, 3) ---
+        ╙── 4 ╾ 1, 2, 3
+            ├─╼ 1 ╾ 1, 2, 3
+            │   ├─╼ 2 ╾ 2, 3, 4
+            │   │   ├─╼ 3 ╾ 1, 3, 4
+            │   │   │   └─╼  ...
+            │   │   └─╼  ...
+            │   └─╼  ...
+            └─╼  ...
+        --- add_edge(4, 4) ---
+        ╙── 1 ╾ 1, 2, 3, 4
+            ├─╼ 2 ╾ 2, 3, 4
+            │   ├─╼ 3 ╾ 1, 3, 4
+            │   │   ├─╼ 4 ╾ 1, 2, 4
+            │   │   │   └─╼  ...
+            │   │   └─╼  ...
+            │   └─╼  ...
+            └─╼  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_iterative_add_undirected_edges():
+    """
+    Walk through the cases going from a disconnected to fully connected graph
+    """
+    graph = nx.Graph()
+    graph.add_nodes_from([1, 2, 3, 4])
+    lines = []
+    write = lines.append
+    write("--- initial state ---")
+    nx.write_network_text(graph, path=write, end="")
+    for i, j in product(graph.nodes, graph.nodes):
+        if i == j:
+            continue
+        write(f"--- add_edge({i}, {j}) ---")
+        graph.add_edge(i, j)
+        nx.write_network_text(graph, path=write, end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        --- initial state ---
+        ╟── 1
+        ╟── 2
+        ╟── 3
+        ╙── 4
+        --- add_edge(1, 2) ---
+        ╟── 3
+        ╟── 4
+        ╙── 1
+            └── 2
+        --- add_edge(1, 3) ---
+        ╟── 4
+        ╙── 2
+            └── 1
+                └── 3
+        --- add_edge(1, 4) ---
+        ╙── 2
+            └── 1
+                ├── 3
+                └── 4
+        --- add_edge(2, 1) ---
+        ╙── 2
+            └── 1
+                ├── 3
+                └── 4
+        --- add_edge(2, 3) ---
+        ╙── 4
+            └── 1
+                ├── 2
+                │   └── 3 ─ 1
+                └──  ...
+        --- add_edge(2, 4) ---
+        ╙── 3
+            ├── 1
+            │   ├── 2 ─ 3
+            │   │   └── 4 ─ 1
+            │   └──  ...
+            └──  ...
+        --- add_edge(3, 1) ---
+        ╙── 3
+            ├── 1
+            │   ├── 2 ─ 3
+            │   │   └── 4 ─ 1
+            │   └──  ...
+            └──  ...
+        --- add_edge(3, 2) ---
+        ╙── 3
+            ├── 1
+            │   ├── 2 ─ 3
+            │   │   └── 4 ─ 1
+            │   └──  ...
+            └──  ...
+        --- add_edge(3, 4) ---
+        ╙── 1
+            ├── 2
+            │   ├── 3 ─ 1
+            │   │   └── 4 ─ 1, 2
+            │   └──  ...
+            └──  ...
+        --- add_edge(4, 1) ---
+        ╙── 1
+            ├── 2
+            │   ├── 3 ─ 1
+            │   │   └── 4 ─ 1, 2
+            │   └──  ...
+            └──  ...
+        --- add_edge(4, 2) ---
+        ╙── 1
+            ├── 2
+            │   ├── 3 ─ 1
+            │   │   └── 4 ─ 1, 2
+            │   └──  ...
+            └──  ...
+        --- add_edge(4, 3) ---
+        ╙── 1
+            ├── 2
+            │   ├── 3 ─ 1
+            │   │   └── 4 ─ 1, 2
+            │   └──  ...
+            └──  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_iterative_add_random_directed_edges():
+    """
+    Walk through the cases going from a disconnected to fully connected graph
+    """
+
+    rng = random.Random(724466096)
+    graph = nx.DiGraph()
+    graph.add_nodes_from([1, 2, 3, 4, 5])
+    possible_edges = list(product(graph.nodes, graph.nodes))
+    rng.shuffle(possible_edges)
+    graph.add_edges_from(possible_edges[0:8])
+    lines = []
+    write = lines.append
+    write("--- initial state ---")
+    nx.write_network_text(graph, path=write, end="")
+    for i, j in possible_edges[8:12]:
+        write(f"--- add_edge({i}, {j}) ---")
+        graph.add_edge(i, j)
+        nx.write_network_text(graph, path=write, end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        --- initial state ---
+        ╙── 3 ╾ 5
+            └─╼ 2 ╾ 2
+                ├─╼ 4 ╾ 4
+                │   ├─╼ 5
+                │   │   ├─╼ 1 ╾ 1
+                │   │   │   └─╼  ...
+                │   │   └─╼  ...
+                │   └─╼  ...
+                └─╼  ...
+        --- add_edge(4, 1) ---
+        ╙── 3 ╾ 5
+            └─╼ 2 ╾ 2
+                ├─╼ 4 ╾ 4
+                │   ├─╼ 5
+                │   │   ├─╼ 1 ╾ 1, 4
+                │   │   │   └─╼  ...
+                │   │   └─╼  ...
+                │   └─╼  ...
+                └─╼  ...
+        --- add_edge(2, 1) ---
+        ╙── 3 ╾ 5
+            └─╼ 2 ╾ 2
+                ├─╼ 4 ╾ 4
+                │   ├─╼ 5
+                │   │   ├─╼ 1 ╾ 1, 4, 2
+                │   │   │   └─╼  ...
+                │   │   └─╼  ...
+                │   └─╼  ...
+                └─╼  ...
+        --- add_edge(5, 2) ---
+        ╙── 3 ╾ 5
+            └─╼ 2 ╾ 2, 5
+                ├─╼ 4 ╾ 4
+                │   ├─╼ 5
+                │   │   ├─╼ 1 ╾ 1, 4, 2
+                │   │   │   └─╼  ...
+                │   │   └─╼  ...
+                │   └─╼  ...
+                └─╼  ...
+        --- add_edge(1, 5) ---
+        ╙── 3 ╾ 5
+            └─╼ 2 ╾ 2, 5
+                ├─╼ 4 ╾ 4
+                │   ├─╼ 5 ╾ 1
+                │   │   ├─╼ 1 ╾ 1, 4, 2
+                │   │   │   └─╼  ...
+                │   │   └─╼  ...
+                │   └─╼  ...
+                └─╼  ...
+
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_nearly_forest():
+    g = nx.DiGraph()
+    g.add_edge(1, 2)
+    g.add_edge(1, 5)
+    g.add_edge(2, 3)
+    g.add_edge(3, 4)
+    g.add_edge(5, 6)
+    g.add_edge(6, 7)
+    g.add_edge(6, 8)
+    orig = g.copy()
+    g.add_edge(1, 8)  # forward edge
+    g.add_edge(4, 2)  # back edge
+    g.add_edge(6, 3)  # cross edge
+    lines = []
+    write = lines.append
+    write("--- directed case ---")
+    nx.write_network_text(orig, path=write, end="")
+    write("--- add (1, 8), (4, 2), (6, 3) ---")
+    nx.write_network_text(g, path=write, end="")
+    write("--- undirected case ---")
+    nx.write_network_text(orig.to_undirected(), path=write, sources=[1], end="")
+    write("--- add (1, 8), (4, 2), (6, 3) ---")
+    nx.write_network_text(g.to_undirected(), path=write, sources=[1], end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        --- directed case ---
+        ╙── 1
+            ├─╼ 2
+            │   └─╼ 3
+            │       └─╼ 4
+            └─╼ 5
+                └─╼ 6
+                    ├─╼ 7
+                    └─╼ 8
+        --- add (1, 8), (4, 2), (6, 3) ---
+        ╙── 1
+            ├─╼ 2 ╾ 4
+            │   └─╼ 3 ╾ 6
+            │       └─╼ 4
+            │           └─╼  ...
+            ├─╼ 5
+            │   └─╼ 6
+            │       ├─╼ 7
+            │       ├─╼ 8 ╾ 1
+            │       └─╼  ...
+            └─╼  ...
+        --- undirected case ---
+        ╙── 1
+            ├── 2
+            │   └── 3
+            │       └── 4
+            └── 5
+                └── 6
+                    ├── 7
+                    └── 8
+        --- add (1, 8), (4, 2), (6, 3) ---
+        ╙── 1
+            ├── 2
+            │   ├── 3
+            │   │   ├── 4 ─ 2
+            │   │   └── 6
+            │   │       ├── 5 ─ 1
+            │   │       ├── 7
+            │   │       └── 8 ─ 1
+            │   └──  ...
+            └──  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_complete_graph_ascii_only():
+    graph = nx.generators.complete_graph(5, create_using=nx.DiGraph)
+    lines = []
+    write = lines.append
+    write("--- directed case ---")
+    nx.write_network_text(graph, path=write, ascii_only=True, end="")
+    write("--- undirected case ---")
+    nx.write_network_text(graph.to_undirected(), path=write, ascii_only=True, end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        --- directed case ---
+        +-- 0 <- 1, 2, 3, 4
+            |-> 1 <- 2, 3, 4
+            |   |-> 2 <- 0, 3, 4
+            |   |   |-> 3 <- 0, 1, 4
+            |   |   |   |-> 4 <- 0, 1, 2
+            |   |   |   |   L->  ...
+            |   |   |   L->  ...
+            |   |   L->  ...
+            |   L->  ...
+            L->  ...
+        --- undirected case ---
+        +-- 0
+            |-- 1
+            |   |-- 2 - 0
+            |   |   |-- 3 - 0, 1
+            |   |   |   L-- 4 - 0, 1, 2
+            |   |   L--  ...
+            |   L--  ...
+            L--  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_with_labels():
+    graph = nx.generators.complete_graph(5, create_using=nx.DiGraph)
+    for n in graph.nodes:
+        graph.nodes[n]["label"] = f"Node(n={n})"
+    lines = []
+    write = lines.append
+    nx.write_network_text(graph, path=write, with_labels=True, ascii_only=False, end="")
+    text = "\n".join(lines)
+    # Non trees with labels can get somewhat out of hand with network text
+    # because we need to immediately show every non-tree edge to the right
+    target = dedent(
+        """
+        ╙── Node(n=0) ╾ Node(n=1), Node(n=2), Node(n=3), Node(n=4)
+            ├─╼ Node(n=1) ╾ Node(n=2), Node(n=3), Node(n=4)
+            │   ├─╼ Node(n=2) ╾ Node(n=0), Node(n=3), Node(n=4)
+            │   │   ├─╼ Node(n=3) ╾ Node(n=0), Node(n=1), Node(n=4)
+            │   │   │   ├─╼ Node(n=4) ╾ Node(n=0), Node(n=1), Node(n=2)
+            │   │   │   │   └─╼  ...
+            │   │   │   └─╼  ...
+            │   │   └─╼  ...
+            │   └─╼  ...
+            └─╼  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_complete_graphs():
+    lines = []
+    write = lines.append
+    for k in [0, 1, 2, 3, 4, 5]:
+        g = nx.generators.complete_graph(k)
+        write(f"--- undirected k={k} ---")
+        nx.write_network_text(g, path=write, end="")
+
+    for k in [0, 1, 2, 3, 4, 5]:
+        g = nx.generators.complete_graph(k, nx.DiGraph)
+        write(f"--- directed k={k} ---")
+        nx.write_network_text(g, path=write, end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        --- undirected k=0 ---
+        ╙
+        --- undirected k=1 ---
+        ╙── 0
+        --- undirected k=2 ---
+        ╙── 0
+            └── 1
+        --- undirected k=3 ---
+        ╙── 0
+            ├── 1
+            │   └── 2 ─ 0
+            └──  ...
+        --- undirected k=4 ---
+        ╙── 0
+            ├── 1
+            │   ├── 2 ─ 0
+            │   │   └── 3 ─ 0, 1
+            │   └──  ...
+            └──  ...
+        --- undirected k=5 ---
+        ╙── 0
+            ├── 1
+            │   ├── 2 ─ 0
+            │   │   ├── 3 ─ 0, 1
+            │   │   │   └── 4 ─ 0, 1, 2
+            │   │   └──  ...
+            │   └──  ...
+            └──  ...
+        --- directed k=0 ---
+        ╙
+        --- directed k=1 ---
+        ╙── 0
+        --- directed k=2 ---
+        ╙── 0 ╾ 1
+            └─╼ 1
+                └─╼  ...
+        --- directed k=3 ---
+        ╙── 0 ╾ 1, 2
+            ├─╼ 1 ╾ 2
+            │   ├─╼ 2 ╾ 0
+            │   │   └─╼  ...
+            │   └─╼  ...
+            └─╼  ...
+        --- directed k=4 ---
+        ╙── 0 ╾ 1, 2, 3
+            ├─╼ 1 ╾ 2, 3
+            │   ├─╼ 2 ╾ 0, 3
+            │   │   ├─╼ 3 ╾ 0, 1
+            │   │   │   └─╼  ...
+            │   │   └─╼  ...
+            │   └─╼  ...
+            └─╼  ...
+        --- directed k=5 ---
+        ╙── 0 ╾ 1, 2, 3, 4
+            ├─╼ 1 ╾ 2, 3, 4
+            │   ├─╼ 2 ╾ 0, 3, 4
+            │   │   ├─╼ 3 ╾ 0, 1, 4
+            │   │   │   ├─╼ 4 ╾ 0, 1, 2
+            │   │   │   │   └─╼  ...
+            │   │   │   └─╼  ...
+            │   │   └─╼  ...
+            │   └─╼  ...
+            └─╼  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_multiple_sources():
+    g = nx.DiGraph()
+    g.add_edge(1, 2)
+    g.add_edge(1, 3)
+    g.add_edge(2, 4)
+    g.add_edge(3, 5)
+    g.add_edge(3, 6)
+    g.add_edge(5, 4)
+    g.add_edge(4, 1)
+    g.add_edge(1, 5)
+    lines = []
+    write = lines.append
+    # Use each node as the starting point to demonstrate how the representation
+    # changes.
+    nodes = sorted(g.nodes())
+    for n in nodes:
+        write(f"--- source node: {n} ---")
+        nx.write_network_text(g, path=write, sources=[n], end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        --- source node: 1 ---
+        ╙── 1 ╾ 4
+            ├─╼ 2
+            │   └─╼ 4 ╾ 5
+            │       └─╼  ...
+            ├─╼ 3
+            │   ├─╼ 5 ╾ 1
+            │   │   └─╼  ...
+            │   └─╼ 6
+            └─╼  ...
+        --- source node: 2 ---
+        ╙── 2 ╾ 1
+            └─╼ 4 ╾ 5
+                └─╼ 1
+                    ├─╼ 3
+                    │   ├─╼ 5 ╾ 1
+                    │   │   └─╼  ...
+                    │   └─╼ 6
+                    └─╼  ...
+        --- source node: 3 ---
+        ╙── 3 ╾ 1
+            ├─╼ 5 ╾ 1
+            │   └─╼ 4 ╾ 2
+            │       └─╼ 1
+            │           ├─╼ 2
+            │           │   └─╼  ...
+            │           └─╼  ...
+            └─╼ 6
+        --- source node: 4 ---
+        ╙── 4 ╾ 2, 5
+            └─╼ 1
+                ├─╼ 2
+                │   └─╼  ...
+                ├─╼ 3
+                │   ├─╼ 5 ╾ 1
+                │   │   └─╼  ...
+                │   └─╼ 6
+                └─╼  ...
+        --- source node: 5 ---
+        ╙── 5 ╾ 3, 1
+            └─╼ 4 ╾ 2
+                └─╼ 1
+                    ├─╼ 2
+                    │   └─╼  ...
+                    ├─╼ 3
+                    │   ├─╼ 6
+                    │   └─╼  ...
+                    └─╼  ...
+        --- source node: 6 ---
+        ╙── 6 ╾ 3
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_star_graph():
+    graph = nx.star_graph(5, create_using=nx.Graph)
+    lines = []
+    write = lines.append
+    nx.write_network_text(graph, path=write, end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        ╙── 1
+            └── 0
+                ├── 2
+                ├── 3
+                ├── 4
+                └── 5
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_path_graph():
+    graph = nx.path_graph(3, create_using=nx.Graph)
+    lines = []
+    write = lines.append
+    nx.write_network_text(graph, path=write, end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        ╙── 0
+            └── 1
+                └── 2
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_lollipop_graph():
+    graph = nx.lollipop_graph(4, 2, create_using=nx.Graph)
+    lines = []
+    write = lines.append
+    nx.write_network_text(graph, path=write, end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        ╙── 5
+            └── 4
+                └── 3
+                    ├── 0
+                    │   ├── 1 ─ 3
+                    │   │   └── 2 ─ 0, 3
+                    │   └──  ...
+                    └──  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_wheel_graph():
+    graph = nx.wheel_graph(7, create_using=nx.Graph)
+    lines = []
+    write = lines.append
+    nx.write_network_text(graph, path=write, end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        ╙── 1
+            ├── 0
+            │   ├── 2 ─ 1
+            │   │   └── 3 ─ 0
+            │   │       └── 4 ─ 0
+            │   │           └── 5 ─ 0
+            │   │               └── 6 ─ 0, 1
+            │   └──  ...
+            └──  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_circular_ladder_graph():
+    graph = nx.circular_ladder_graph(4, create_using=nx.Graph)
+    lines = []
+    write = lines.append
+    nx.write_network_text(graph, path=write, end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        ╙── 0
+            ├── 1
+            │   ├── 2
+            │   │   ├── 3 ─ 0
+            │   │   │   └── 7
+            │   │   │       ├── 6 ─ 2
+            │   │   │       │   └── 5 ─ 1
+            │   │   │       │       └── 4 ─ 0, 7
+            │   │   │       └──  ...
+            │   │   └──  ...
+            │   └──  ...
+            └──  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_dorogovtsev_goltsev_mendes_graph():
+    graph = nx.dorogovtsev_goltsev_mendes_graph(4, create_using=nx.Graph)
+    lines = []
+    write = lines.append
+    nx.write_network_text(graph, path=write, end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        ╙── 15
+            ├── 0
+            │   ├── 1 ─ 15
+            │   │   ├── 2 ─ 0
+            │   │   │   ├── 4 ─ 0
+            │   │   │   │   ├── 9 ─ 0
+            │   │   │   │   │   ├── 22 ─ 0
+            │   │   │   │   │   └── 38 ─ 4
+            │   │   │   │   ├── 13 ─ 2
+            │   │   │   │   │   ├── 34 ─ 2
+            │   │   │   │   │   └── 39 ─ 4
+            │   │   │   │   ├── 18 ─ 0
+            │   │   │   │   ├── 30 ─ 2
+            │   │   │   │   └──  ...
+            │   │   │   ├── 5 ─ 1
+            │   │   │   │   ├── 12 ─ 1
+            │   │   │   │   │   ├── 29 ─ 1
+            │   │   │   │   │   └── 40 ─ 5
+            │   │   │   │   ├── 14 ─ 2
+            │   │   │   │   │   ├── 35 ─ 2
+            │   │   │   │   │   └── 41 ─ 5
+            │   │   │   │   ├── 25 ─ 1
+            │   │   │   │   ├── 31 ─ 2
+            │   │   │   │   └──  ...
+            │   │   │   ├── 7 ─ 0
+            │   │   │   │   ├── 20 ─ 0
+            │   │   │   │   └── 32 ─ 2
+            │   │   │   ├── 10 ─ 1
+            │   │   │   │   ├── 27 ─ 1
+            │   │   │   │   └── 33 ─ 2
+            │   │   │   ├── 16 ─ 0
+            │   │   │   ├── 23 ─ 1
+            │   │   │   └──  ...
+            │   │   ├── 3 ─ 0
+            │   │   │   ├── 8 ─ 0
+            │   │   │   │   ├── 21 ─ 0
+            │   │   │   │   └── 36 ─ 3
+            │   │   │   ├── 11 ─ 1
+            │   │   │   │   ├── 28 ─ 1
+            │   │   │   │   └── 37 ─ 3
+            │   │   │   ├── 17 ─ 0
+            │   │   │   ├── 24 ─ 1
+            │   │   │   └──  ...
+            │   │   ├── 6 ─ 0
+            │   │   │   ├── 19 ─ 0
+            │   │   │   └── 26 ─ 1
+            │   │   └──  ...
+            │   └──  ...
+            └──  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_tree_max_depth():
+    orig = nx.balanced_tree(r=1, h=3, create_using=nx.DiGraph)
+    lines = []
+    write = lines.append
+    write("--- directed case, max_depth=0 ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=0)
+    write("--- directed case, max_depth=1 ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=1)
+    write("--- directed case, max_depth=2 ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=2)
+    write("--- directed case, max_depth=3 ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=3)
+    write("--- directed case, max_depth=4 ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=4)
+    write("--- undirected case, max_depth=0 ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=0)
+    write("--- undirected case, max_depth=1 ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=1)
+    write("--- undirected case, max_depth=2 ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=2)
+    write("--- undirected case, max_depth=3 ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=3)
+    write("--- undirected case, max_depth=4 ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=4)
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        --- directed case, max_depth=0 ---
+        ╙ ...
+        --- directed case, max_depth=1 ---
+        ╙── 0
+            └─╼  ...
+        --- directed case, max_depth=2 ---
+        ╙── 0
+            └─╼ 1
+                └─╼  ...
+        --- directed case, max_depth=3 ---
+        ╙── 0
+            └─╼ 1
+                └─╼ 2
+                    └─╼  ...
+        --- directed case, max_depth=4 ---
+        ╙── 0
+            └─╼ 1
+                └─╼ 2
+                    └─╼ 3
+        --- undirected case, max_depth=0 ---
+        ╙ ...
+        --- undirected case, max_depth=1 ---
+        ╙── 0 ─ 1
+            └──  ...
+        --- undirected case, max_depth=2 ---
+        ╙── 0
+            └── 1 ─ 2
+                └──  ...
+        --- undirected case, max_depth=3 ---
+        ╙── 0
+            └── 1
+                └── 2 ─ 3
+                    └──  ...
+        --- undirected case, max_depth=4 ---
+        ╙── 0
+            └── 1
+                └── 2
+                    └── 3
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_graph_max_depth():
+    orig = nx.erdos_renyi_graph(10, 0.15, directed=True, seed=40392)
+    lines = []
+    write = lines.append
+    write("--- directed case, max_depth=None ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=None)
+    write("--- directed case, max_depth=0 ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=0)
+    write("--- directed case, max_depth=1 ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=1)
+    write("--- directed case, max_depth=2 ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=2)
+    write("--- directed case, max_depth=3 ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=3)
+    write("--- undirected case, max_depth=None ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=None)
+    write("--- undirected case, max_depth=0 ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=0)
+    write("--- undirected case, max_depth=1 ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=1)
+    write("--- undirected case, max_depth=2 ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=2)
+    write("--- undirected case, max_depth=3 ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=3)
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        --- directed case, max_depth=None ---
+        ╟── 4
+        ╎   ├─╼ 0 ╾ 3
+        ╎   ├─╼ 5 ╾ 7
+        ╎   │   └─╼ 3
+        ╎   │       ├─╼ 1 ╾ 9
+        ╎   │       │   └─╼ 9 ╾ 6
+        ╎   │       │       ├─╼ 6
+        ╎   │       │       │   └─╼  ...
+        ╎   │       │       ├─╼ 7 ╾ 4
+        ╎   │       │       │   ├─╼ 2
+        ╎   │       │       │   └─╼  ...
+        ╎   │       │       └─╼  ...
+        ╎   │       └─╼  ...
+        ╎   └─╼  ...
+        ╙── 8
+        --- directed case, max_depth=0 ---
+        ╙ ...
+        --- directed case, max_depth=1 ---
+        ╟── 4
+        ╎   └─╼  ...
+        ╙── 8
+        --- directed case, max_depth=2 ---
+        ╟── 4
+        ╎   ├─╼ 0 ╾ 3
+        ╎   ├─╼ 5 ╾ 7
+        ╎   │   └─╼  ...
+        ╎   └─╼ 7 ╾ 9
+        ╎       └─╼  ...
+        ╙── 8
+        --- directed case, max_depth=3 ---
+        ╟── 4
+        ╎   ├─╼ 0 ╾ 3
+        ╎   ├─╼ 5 ╾ 7
+        ╎   │   └─╼ 3
+        ╎   │       └─╼  ...
+        ╎   └─╼ 7 ╾ 9
+        ╎       ├─╼ 2
+        ╎       └─╼  ...
+        ╙── 8
+        --- undirected case, max_depth=None ---
+        ╟── 8
+        ╙── 2
+            └── 7
+                ├── 4
+                │   ├── 0
+                │   │   └── 3
+                │   │       ├── 1
+                │   │       │   └── 9 ─ 7
+                │   │       │       └── 6
+                │   │       └── 5 ─ 4, 7
+                │   └──  ...
+                └──  ...
+        --- undirected case, max_depth=0 ---
+        ╙ ...
+        --- undirected case, max_depth=1 ---
+        ╟── 8
+        ╙── 2 ─ 7
+            └──  ...
+        --- undirected case, max_depth=2 ---
+        ╟── 8
+        ╙── 2
+            └── 7 ─ 4, 5, 9
+                └──  ...
+        --- undirected case, max_depth=3 ---
+        ╟── 8
+        ╙── 2
+            └── 7
+                ├── 4 ─ 0, 5
+                │   └──  ...
+                ├── 5 ─ 4, 3
+                │   └──  ...
+                └── 9 ─ 1, 6
+                    └──  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_clique_max_depth():
+    orig = nx.complete_graph(5, nx.DiGraph)
+    lines = []
+    write = lines.append
+    write("--- directed case, max_depth=None ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=None)
+    write("--- directed case, max_depth=0 ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=0)
+    write("--- directed case, max_depth=1 ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=1)
+    write("--- directed case, max_depth=2 ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=2)
+    write("--- directed case, max_depth=3 ---")
+    nx.write_network_text(orig, path=write, end="", max_depth=3)
+    write("--- undirected case, max_depth=None ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=None)
+    write("--- undirected case, max_depth=0 ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=0)
+    write("--- undirected case, max_depth=1 ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=1)
+    write("--- undirected case, max_depth=2 ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=2)
+    write("--- undirected case, max_depth=3 ---")
+    nx.write_network_text(orig.to_undirected(), path=write, end="", max_depth=3)
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        --- directed case, max_depth=None ---
+        ╙── 0 ╾ 1, 2, 3, 4
+            ├─╼ 1 ╾ 2, 3, 4
+            │   ├─╼ 2 ╾ 0, 3, 4
+            │   │   ├─╼ 3 ╾ 0, 1, 4
+            │   │   │   ├─╼ 4 ╾ 0, 1, 2
+            │   │   │   │   └─╼  ...
+            │   │   │   └─╼  ...
+            │   │   └─╼  ...
+            │   └─╼  ...
+            └─╼  ...
+        --- directed case, max_depth=0 ---
+        ╙ ...
+        --- directed case, max_depth=1 ---
+        ╙── 0 ╾ 1, 2, 3, 4
+            └─╼  ...
+        --- directed case, max_depth=2 ---
+        ╙── 0 ╾ 1, 2, 3, 4
+            ├─╼ 1 ╾ 2, 3, 4
+            │   └─╼  ...
+            ├─╼ 2 ╾ 1, 3, 4
+            │   └─╼  ...
+            ├─╼ 3 ╾ 1, 2, 4
+            │   └─╼  ...
+            └─╼ 4 ╾ 1, 2, 3
+                └─╼  ...
+        --- directed case, max_depth=3 ---
+        ╙── 0 ╾ 1, 2, 3, 4
+            ├─╼ 1 ╾ 2, 3, 4
+            │   ├─╼ 2 ╾ 0, 3, 4
+            │   │   └─╼  ...
+            │   ├─╼ 3 ╾ 0, 2, 4
+            │   │   └─╼  ...
+            │   ├─╼ 4 ╾ 0, 2, 3
+            │   │   └─╼  ...
+            │   └─╼  ...
+            └─╼  ...
+        --- undirected case, max_depth=None ---
+        ╙── 0
+            ├── 1
+            │   ├── 2 ─ 0
+            │   │   ├── 3 ─ 0, 1
+            │   │   │   └── 4 ─ 0, 1, 2
+            │   │   └──  ...
+            │   └──  ...
+            └──  ...
+        --- undirected case, max_depth=0 ---
+        ╙ ...
+        --- undirected case, max_depth=1 ---
+        ╙── 0 ─ 1, 2, 3, 4
+            └──  ...
+        --- undirected case, max_depth=2 ---
+        ╙── 0
+            ├── 1 ─ 2, 3, 4
+            │   └──  ...
+            ├── 2 ─ 1, 3, 4
+            │   └──  ...
+            ├── 3 ─ 1, 2, 4
+            │   └──  ...
+            └── 4 ─ 1, 2, 3
+        --- undirected case, max_depth=3 ---
+        ╙── 0
+            ├── 1
+            │   ├── 2 ─ 0, 3, 4
+            │   │   └──  ...
+            │   ├── 3 ─ 0, 2, 4
+            │   │   └──  ...
+            │   └── 4 ─ 0, 2, 3
+            └──  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_custom_label():
+    # Create a directed forest with labels
+    graph = nx.erdos_renyi_graph(5, 0.4, directed=True, seed=359222358)
+    for node in graph.nodes:
+        graph.nodes[node]["label"] = f"Node({node})"
+        graph.nodes[node]["chr"] = chr(node + ord("a") - 1)
+        if node % 2 == 0:
+            graph.nodes[node]["part"] = chr(node + ord("a"))
+
+    lines = []
+    write = lines.append
+    write("--- when with_labels=True, uses the 'label' attr ---")
+    nx.write_network_text(graph, path=write, with_labels=True, end="", max_depth=None)
+    write("--- when with_labels=False, uses str(node) value ---")
+    nx.write_network_text(graph, path=write, with_labels=False, end="", max_depth=None)
+    write("--- when with_labels is a string, use that attr ---")
+    nx.write_network_text(graph, path=write, with_labels="chr", end="", max_depth=None)
+    write("--- fallback to str(node) when the attr does not exist ---")
+    nx.write_network_text(graph, path=write, with_labels="part", end="", max_depth=None)
+
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        --- when with_labels=True, uses the 'label' attr ---
+        ╙── Node(1)
+            └─╼ Node(3) ╾ Node(2)
+                ├─╼ Node(0)
+                │   ├─╼ Node(2) ╾ Node(3), Node(4)
+                │   │   └─╼  ...
+                │   └─╼ Node(4)
+                │       └─╼  ...
+                └─╼  ...
+        --- when with_labels=False, uses str(node) value ---
+        ╙── 1
+            └─╼ 3 ╾ 2
+                ├─╼ 0
+                │   ├─╼ 2 ╾ 3, 4
+                │   │   └─╼  ...
+                │   └─╼ 4
+                │       └─╼  ...
+                └─╼  ...
+        --- when with_labels is a string, use that attr ---
+        ╙── a
+            └─╼ c ╾ b
+                ├─╼ `
+                │   ├─╼ b ╾ c, d
+                │   │   └─╼  ...
+                │   └─╼ d
+                │       └─╼  ...
+                └─╼  ...
+        --- fallback to str(node) when the attr does not exist ---
+        ╙── 1
+            └─╼ 3 ╾ c
+                ├─╼ a
+                │   ├─╼ c ╾ 3, e
+                │   │   └─╼  ...
+                │   └─╼ e
+                │       └─╼  ...
+                └─╼  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_write_network_text_vertical_chains():
+    graph1 = nx.lollipop_graph(4, 2, create_using=nx.Graph)
+    graph1.add_edge(0, -1)
+    graph1.add_edge(-1, -2)
+    graph1.add_edge(-2, -3)
+
+    graph2 = graph1.to_directed()
+    graph2.remove_edges_from([(u, v) for u, v in graph2.edges if v > u])
+
+    lines = []
+    write = lines.append
+    write("--- Undirected UTF ---")
+    nx.write_network_text(graph1, path=write, end="", vertical_chains=True)
+    write("--- Undirected ASCI ---")
+    nx.write_network_text(
+        graph1, path=write, end="", vertical_chains=True, ascii_only=True
+    )
+    write("--- Directed UTF ---")
+    nx.write_network_text(graph2, path=write, end="", vertical_chains=True)
+    write("--- Directed ASCI ---")
+    nx.write_network_text(
+        graph2, path=write, end="", vertical_chains=True, ascii_only=True
+    )
+
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        --- Undirected UTF ---
+        ╙── 5
+            │
+            4
+            │
+            3
+            ├── 0
+            │   ├── 1 ─ 3
+            │   │   │
+            │   │   2 ─ 0, 3
+            │   ├── -1
+            │   │   │
+            │   │   -2
+            │   │   │
+            │   │   -3
+            │   └──  ...
+            └──  ...
+        --- Undirected ASCI ---
+        +-- 5
+            |
+            4
+            |
+            3
+            |-- 0
+            |   |-- 1 - 3
+            |   |   |
+            |   |   2 - 0, 3
+            |   |-- -1
+            |   |   |
+            |   |   -2
+            |   |   |
+            |   |   -3
+            |   L--  ...
+            L--  ...
+        --- Directed UTF ---
+        ╙── 5
+            ╽
+            4
+            ╽
+            3
+            ├─╼ 0 ╾ 1, 2
+            │   ╽
+            │   -1
+            │   ╽
+            │   -2
+            │   ╽
+            │   -3
+            ├─╼ 1 ╾ 2
+            │   └─╼  ...
+            └─╼ 2
+                └─╼  ...
+        --- Directed ASCI ---
+        +-- 5
+            !
+            4
+            !
+            3
+            |-> 0 <- 1, 2
+            |   !
+            |   -1
+            |   !
+            |   -2
+            |   !
+            |   -3
+            |-> 1 <- 2
+            |   L->  ...
+            L-> 2
+                L->  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_collapse_directed():
+    graph = nx.balanced_tree(r=2, h=3, create_using=nx.DiGraph)
+    lines = []
+    write = lines.append
+    write("--- Original ---")
+    nx.write_network_text(graph, path=write, end="")
+    graph.nodes[1]["collapse"] = True
+    write("--- Collapse Node 1 ---")
+    nx.write_network_text(graph, path=write, end="")
+    write("--- Add alternate path (5, 3) to collapsed zone")
+    graph.add_edge(5, 3)
+    nx.write_network_text(graph, path=write, end="")
+    write("--- Collapse Node 0 ---")
+    graph.nodes[0]["collapse"] = True
+    nx.write_network_text(graph, path=write, end="")
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        --- Original ---
+        ╙── 0
+            ├─╼ 1
+            │   ├─╼ 3
+            │   │   ├─╼ 7
+            │   │   └─╼ 8
+            │   └─╼ 4
+            │       ├─╼ 9
+            │       └─╼ 10
+            └─╼ 2
+                ├─╼ 5
+                │   ├─╼ 11
+                │   └─╼ 12
+                └─╼ 6
+                    ├─╼ 13
+                    └─╼ 14
+        --- Collapse Node 1 ---
+        ╙── 0
+            ├─╼ 1
+            │   └─╼  ...
+            └─╼ 2
+                ├─╼ 5
+                │   ├─╼ 11
+                │   └─╼ 12
+                └─╼ 6
+                    ├─╼ 13
+                    └─╼ 14
+        --- Add alternate path (5, 3) to collapsed zone
+        ╙── 0
+            ├─╼ 1
+            │   └─╼  ...
+            └─╼ 2
+                ├─╼ 5
+                │   ├─╼ 11
+                │   ├─╼ 12
+                │   └─╼ 3 ╾ 1
+                │       ├─╼ 7
+                │       └─╼ 8
+                └─╼ 6
+                    ├─╼ 13
+                    └─╼ 14
+        --- Collapse Node 0 ---
+        ╙── 0
+            └─╼  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def test_collapse_undirected():
+    graph = nx.balanced_tree(r=2, h=3, create_using=nx.Graph)
+    lines = []
+    write = lines.append
+    write("--- Original ---")
+    nx.write_network_text(graph, path=write, end="", sources=[0])
+    graph.nodes[1]["collapse"] = True
+    write("--- Collapse Node 1 ---")
+    nx.write_network_text(graph, path=write, end="", sources=[0])
+    write("--- Add alternate path (5, 3) to collapsed zone")
+    graph.add_edge(5, 3)
+    nx.write_network_text(graph, path=write, end="", sources=[0])
+    write("--- Collapse Node 0 ---")
+    graph.nodes[0]["collapse"] = True
+    nx.write_network_text(graph, path=write, end="", sources=[0])
+    text = "\n".join(lines)
+    target = dedent(
+        """
+        --- Original ---
+        ╙── 0
+            ├── 1
+            │   ├── 3
+            │   │   ├── 7
+            │   │   └── 8
+            │   └── 4
+            │       ├── 9
+            │       └── 10
+            └── 2
+                ├── 5
+                │   ├── 11
+                │   └── 12
+                └── 6
+                    ├── 13
+                    └── 14
+        --- Collapse Node 1 ---
+        ╙── 0
+            ├── 1 ─ 3, 4
+            │   └──  ...
+            └── 2
+                ├── 5
+                │   ├── 11
+                │   └── 12
+                └── 6
+                    ├── 13
+                    └── 14
+        --- Add alternate path (5, 3) to collapsed zone
+        ╙── 0
+            ├── 1 ─ 3, 4
+            │   └──  ...
+            └── 2
+                ├── 5
+                │   ├── 11
+                │   ├── 12
+                │   └── 3 ─ 1
+                │       ├── 7
+                │       └── 8
+                └── 6
+                    ├── 13
+                    └── 14
+        --- Collapse Node 0 ---
+        ╙── 0 ─ 1, 2
+            └──  ...
+        """
+    ).strip()
+    assert target == text
+
+
+def generate_test_graphs():
+    """
+    Generate a gauntlet of different test graphs with different properties
+    """
+    import random
+
+    rng = random.Random(976689776)
+    num_randomized = 3
+
+    for directed in [0, 1]:
+        cls = nx.DiGraph if directed else nx.Graph
+
+        for num_nodes in range(17):
+            # Disconnected graph
+            graph = cls()
+            graph.add_nodes_from(range(num_nodes))
+            yield graph
+
+            # Randomize graphs
+            if num_nodes > 0:
+                for p in [0.1, 0.3, 0.5, 0.7, 0.9]:
+                    for seed in range(num_randomized):
+                        graph = nx.erdos_renyi_graph(
+                            num_nodes, p, directed=directed, seed=rng
+                        )
+                        yield graph
+
+                yield nx.complete_graph(num_nodes, cls)
+
+        yield nx.path_graph(3, create_using=cls)
+        yield nx.balanced_tree(r=1, h=3, create_using=cls)
+        if not directed:
+            yield nx.circular_ladder_graph(4, create_using=cls)
+            yield nx.star_graph(5, create_using=cls)
+            yield nx.lollipop_graph(4, 2, create_using=cls)
+            yield nx.wheel_graph(7, create_using=cls)
+            yield nx.dorogovtsev_goltsev_mendes_graph(4, create_using=cls)
+
+
+@pytest.mark.parametrize(
+    ("vertical_chains", "ascii_only"),
+    tuple(
+        [
+            (vertical_chains, ascii_only)
+            for vertical_chains in [0, 1]
+            for ascii_only in [0, 1]
+        ]
+    ),
+)
+def test_network_text_round_trip(vertical_chains, ascii_only):
+    """
+    Write the graph to network text format, then parse it back in, assert it is
+    the same as the original graph. Passing this test is strong validation of
+    both the format generator and parser.
+    """
+    from networkx.readwrite.text import _parse_network_text
+
+    for graph in generate_test_graphs():
+        graph = nx.relabel_nodes(graph, {n: str(n) for n in graph.nodes})
+        lines = list(
+            nx.generate_network_text(
+                graph, vertical_chains=vertical_chains, ascii_only=ascii_only
+            )
+        )
+        new = _parse_network_text(lines)
+        try:
+            assert new.nodes == graph.nodes
+            assert new.edges == graph.edges
+        except Exception:
+            nx.write_network_text(graph)
+            raise