Fix pylint and mypy errors

* gn3/db/sample_data.py (get_trait_csv_sample_data): Pass __query
directly to cursor.execute.  Rename value to _value in for loop to
make mypy pass.
* gn3/db_utils.py (Connection): Add class docstring.
(Connection.cursor): Add docstring.
* mypy.ini: Add an entry for xapian.

1 files changed, 2 insertions, 0 deletions

diff --git a/gn3/db_utils.py b/gn3/db_utils.py
index 4fd3666..23a570b 100644
--- a/gn3/db_utils.py
+++ b/gn3/db_utils.py
@@ -27,7 +27,9 @@ def database_connector() -> mdb.Connection:
 
 # pylint: disable=missing-class-docstring, missing-function-docstring, too-few-public-methods
 class Connection(Protocol):
+    """Type Annotation for MySQLdb's connection object"""
     def cursor(self) -> Any:
+        """A cursor in which queries may be performed"""
         ...