Add KuzuQAChain (#6454)

This PR adds `KuzuGraph` and `KuzuQAChain` for interacting with [Kùzu
database](https://github.com/kuzudb/kuzu). Kùzu is an in-process
property graph database management system (GDBMS) built for query speed
and scalability. The `KuzuGraph` and `KuzuQAChain` provide the same
functionality as the existing integration with NebulaGraph and Neo4j and
enables query generation and question answering over Kùzu database.

A notebook example and a simple test case have also been added.

---------

Co-authored-by: Dev 2049 <dev.dev2049@gmail.com>

tests/integration_tests/test_kuzu.py

@@ -0,0 +1,56 @@
+import shutil
+import tempfile
+import unittest
+
+from langchain.graphs import KuzuGraph
+
+EXPECTED_SCHEMA = """
+Node properties: [{'properties': [('name', 'STRING')], 'label': 'Movie'}, {'properties': [('name', 'STRING'), ('birthDate', 'STRING')], 'label': 'Person'}]
+Relationships properties: [{'properties': [], 'label': 'ActedIn'}]
+Relationships: ['(:Person)-[:ActedIn]->(:Movie)']
+"""  # noqa: E501
+
+
+class TestKuzu(unittest.TestCase):
+    def setUp(self) -> None:
+        try:
+            import kuzu
+        except ImportError as e:
+            raise ImportError(
+                "Cannot import Python package kuzu. Please install it by running "
+                "`pip install kuzu`."
+            ) from e
+
+        self.tmpdir = tempfile.mkdtemp()
+        self.kuzu_database = kuzu.Database(self.tmpdir)
+        self.conn = kuzu.Connection(self.kuzu_database)
+        self.conn.execute("CREATE NODE TABLE Movie (name STRING, PRIMARY KEY(name))")
+        self.conn.execute("CREATE (:Movie {name: 'The Godfather'})")
+        self.conn.execute("CREATE (:Movie {name: 'The Godfather: Part II'})")
+        self.conn.execute(
+            "CREATE (:Movie {name: 'The Godfather Coda: The Death of Michael "
+            "Corleone'})"
+        )
+        self.kuzu_graph = KuzuGraph(self.kuzu_database)
+
+    def tearDown(self) -> None:
+        shutil.rmtree(self.tmpdir, ignore_errors=True)
+
+    def test_query(self) -> None:
+        result = self.kuzu_graph.query("MATCH (n:Movie) RETURN n.name ORDER BY n.name")
+        excepted_result = [
+            {"n.name": "The Godfather"},
+            {"n.name": "The Godfather Coda: The Death of Michael Corleone"},
+            {"n.name": "The Godfather: Part II"},
+        ]
+        self.assertEqual(result, excepted_result)
+
+    def test_refresh_schema(self) -> None:
+        self.conn.execute(
+            "CREATE NODE TABLE Person (name STRING, birthDate STRING, PRIMARY "
+            "KEY(name))"
+        )
+        self.conn.execute("CREATE REL TABLE ActedIn (FROM Person TO Movie)")
+        self.kuzu_graph.refresh_schema()
+        schema = self.kuzu_graph.get_schema
+        self.assertEqual(schema, EXPECTED_SCHEMA)