Add option to save/load graph cypher QA (#6219)

Similar as https://github.com/hwchase17/langchain/pull/5818

Added the functionality to save/load Graph Cypher QA Chain due to a user
reporting the following error

> raise NotImplementedError("Saving not supported for this chain
type.")\nNotImplementedError: Saving not supported for this chain
type.\n'

tests/integration_tests/chains/test_graph_database.py

@@ -2,6 +2,7 @@
 import os
 
 from langchain.chains.graph_qa.cypher import GraphCypherQAChain
+from langchain.chains.loading import load_chain
 from langchain.graphs import Neo4jGraph
 from langchain.llms.openai import OpenAI
 
@@ -168,3 +169,31 @@ def test_cypher_return_direct() -> None:
     output = chain.run("Who played in Pulp Fiction?")
     expected_output = [{"a.name": "Bruce Willis"}]
     assert output == expected_output
+
+
+def test_cypher_save_load() -> None:
+    """Test saving and loading."""
+
+    FILE_PATH = "cypher.yaml"
+
+    url = os.environ.get("NEO4J_URL")
+    username = os.environ.get("NEO4J_USERNAME")
+    password = os.environ.get("NEO4J_PASSWORD")
+    assert url is not None
+    assert username is not None
+    assert password is not None
+
+    graph = Neo4jGraph(
+        url=url,
+        username=username,
+        password=password,
+    )
+
+    chain = GraphCypherQAChain.from_llm(
+        OpenAI(temperature=0), graph=graph, return_direct=True
+    )
+
+    chain.save(file_path=FILE_PATH)
+    qa_loaded = load_chain(FILE_PATH, graph=graph)
+
+    assert qa_loaded == chain