Add optional Cypher validation tool (#11078)

LLMs have trouble with consistently getting the relationship direction
accurately. That's why I organized a competition how to best and most
simple to fix it based on the existing schema as a post-processing step.
https://github.com/tomasonjo/cypher-direction-competition

I am adding the winner's code in this PR:
https://github.com/sakusaku-rich/cypher-direction-competition

docs/extras/use_cases/more/graph/graph_cypher_qa.ipynb

@@ -48,7 +48,16 @@
    "execution_count": 2,
    "id": "0928915d",
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "/home/tomaz/neo4j/langchain/libs/langchain/langchain/graphs/neo4j_graph.py:52: ExperimentalWarning: The configuration may change in the future.\n",
+      "  self._driver.verify_connectivity()\n"
+     ]
+    }
+   ],
    "source": [
     "graph = Neo4jGraph(\n",
     "    url=\"bolt://localhost:7687\", username=\"neo4j\", password=\"pleaseletmein\"\n",
@@ -558,6 +567,75 @@
     "# Inspect graph schema\n",
     "print(chain.graph_schema)"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "f0202e88-d700-40ed-aef9-0c969c7bf951",
+   "metadata": {},
+   "source": [
+    "# Validate generated Cypher statements\n",
+    "You can use the `validate_cypher` parameter to validate and correct relationship directions in generated Cypher statements"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 20,
+   "id": "53665d03-7afd-433c-bdd5-750127bfb152",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "chain = GraphCypherQAChain.from_llm(\n",
+    "     llm=ChatOpenAI(temperature=0, model=\"gpt-3.5-turbo\"),\n",
+    "     graph=graph,\n",
+    "     verbose=True,\n",
+    "     validate_cypher=True\n",
+    ")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 21,
+   "id": "19e1a591-9c10-4d7b-aa36-a5e1b778a97b",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "\n",
+      "\n",
+      "\u001b[1m> Entering new GraphCypherQAChain chain...\u001b[0m\n",
+      "Generated Cypher:\n",
+      "\u001b[32;1m\u001b[1;3mMATCH (a:Actor)-[:ACTED_IN]->(m:Movie {name: 'Top Gun'})\n",
+      "RETURN a.name\u001b[0m\n",
+      "Full Context:\n",
+      "\u001b[32;1m\u001b[1;3m[{'a.name': 'Tom Cruise'}, {'a.name': 'Val Kilmer'}, {'a.name': 'Anthony Edwards'}, {'a.name': 'Meg Ryan'}]\u001b[0m\n",
+      "\n",
+      "\u001b[1m> Finished chain.\u001b[0m\n"
+     ]
+    },
+    {
+     "data": {
+      "text/plain": [
+       "'Tom Cruise, Val Kilmer, Anthony Edwards, and Meg Ryan played in Top Gun.'"
+      ]
+     },
+     "execution_count": 21,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "chain.run(\"Who played in Top Gun?\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "3fa3f3d5-f7e7-4ca9-8f07-ca22b897f192",
+   "metadata": {},
+   "outputs": [],
+   "source": []
   }
  ],
  "metadata": {