two version of R2R are hereHEADmaster

1 files changed, 1531 insertions, 0 deletions

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": ""}