Templates (#12294)

Co-authored-by: Harrison Chase <hw.chase.17@gmail.com>
Co-authored-by: Lance Martin <lance@langchain.dev>
Co-authored-by: Jacob Lee <jacoblee93@gmail.com>

templates/neo4j-cypher/neo4j_cypher/__init__.py

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+from neo4j_cypher.chain import chain
+
+__all__ = ["chain"]

templates/neo4j-cypher/neo4j_cypher/chain.py

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+from langchain.chat_models import ChatOpenAI
+from langchain.graphs import Neo4jGraph
+from langchain.prompts import ChatPromptTemplate
+from langchain.schema.output_parser import StrOutputParser
+from langchain.schema.runnable import RunnablePassthrough
+from langchain.chains.graph_qa.cypher_utils import CypherQueryCorrector, Schema
+
+# Connection to Neo4j
+graph = Neo4jGraph()
+
+# Cypher validation tool for relationship directions
+corrector_schema = [
+    Schema(el["start"], el["type"], el["end"])
+    for el in graph.structured_schema.get("relationships")
+]
+cypher_validation = CypherQueryCorrector(corrector_schema)
+
+# LLMs
+cypher_llm = ChatOpenAI(model_name="gpt-4", temperature=0.0)
+qa_llm = ChatOpenAI(model_name="gpt-3.5-turbo", temperature=0.0)
+
+# Generate Cypher statement based on natural language input
+cypher_template = """Based on the Neo4j graph schema below, write a Cypher query that would answer the user's question:
+{schema}
+
+Question: {question}
+Cypher query:"""
+
+cypher_prompt = ChatPromptTemplate.from_messages(
+    [
+        (
+            "system",
+            "Given an input question, convert it to a Cypher query. No pre-amble.",
+        ),
+        ("human", cypher_template),
+    ]
+)
+
+cypher_response = (
+    RunnablePassthrough.assign(
+        schema=lambda _: graph.get_schema,
+    )
+    | cypher_prompt
+    | cypher_llm.bind(stop=["\nCypherResult:"])
+    | StrOutputParser()
+)
+
+# Generate natural language response based on database results
+response_template = """Based on the the question, Cypher query, and Cypher response, write a natural language response:
+Question: {question}
+Cypher query: {query}
+Cypher Response: {response}"""
+
+response_prompt = ChatPromptTemplate.from_messages(
+    [
+        (
+            "system",
+            "Given an input question and Cypher response, convert it to a natural language answer. No pre-amble.",
+        ),
+        ("human", response_template),
+    ]
+)
+
+chain = (
+    RunnablePassthrough.assign(query=cypher_response)
+    | RunnablePassthrough.assign(
+        response=lambda x: graph.query(cypher_validation(x["query"])),
+    )
+    | response_prompt
+    | qa_llm
+    | StrOutputParser()
+)