community[patch]: Improve Kuzu Cypher generation prompt (#20481)

- [x] **PR title**: "community: improve kuzu cypher generation prompt"

- [x] **PR message**: ***Delete this entire checklist*** and replace
with
- **Description:** Improves the Kùzu Cypher generation prompt to be more
robust to open source LLM outputs
    - **Issue:** N/A
    - **Dependencies:** N/A
    - **Twitter handle:** @kuzudb

- [x] **Add tests and docs**: If you're adding a new integration, please
include
No new tests (non-breaking. change)

- [x] **Lint and test**: Run `make format`, `make lint` and `make test`
from the root of the package(s) you've modified. See contribution
guidelines for more: https://python.langchain.com/docs/contributing/

libs/langchain/langchain/chains/graph_qa/kuzu.py

@@ -1,6 +1,7 @@
 """Question answering over a graph."""
 from __future__ import annotations
 
+import re
 from typing import Any, Dict, List, Optional
 
 from langchain_community.graphs.kuzu_graph import KuzuGraph
@@ -14,6 +15,30 @@ from langchain.chains.graph_qa.prompts import CYPHER_QA_PROMPT, KUZU_GENERATION_
 from langchain.chains.llm import LLMChain
 
 
+def remove_prefix(text: str, prefix: str) -> str:
+    if text.startswith(prefix):
+        return text[len(prefix) :]
+    return text
+
+
+def extract_cypher(text: str) -> str:
+    """Extract Cypher code from a text.
+
+    Args:
+        text: Text to extract Cypher code from.
+
+    Returns:
+        Cypher code extracted from the text.
+    """
+    # The pattern to find Cypher code enclosed in triple backticks
+    pattern = r"```(.*?)```"
+
+    # Find all matches in the input text
+    matches = re.findall(pattern, text, re.DOTALL)
+
+    return matches[0] if matches else text
+
+
 class KuzuQAChain(Chain):
     """Question-answering against a graph by generating Cypher statements for Kùzu.
 
@@ -84,6 +109,9 @@ class KuzuQAChain(Chain):
         generated_cypher = self.cypher_generation_chain.run(
             {"question": question, "schema": self.graph.get_schema}, callbacks=callbacks
         )
+        # Extract Cypher code if it is wrapped in triple backticks
+        # with the language marker "cypher"
+        generated_cypher = remove_prefix(extract_cypher(generated_cypher), "cypher")
 
         _run_manager.on_text("Generated Cypher:", end="\n", verbose=self.verbose)
         _run_manager.on_text(

libs/langchain/langchain/chains/graph_qa/prompts.py

@@ -76,10 +76,11 @@ NGQL_GENERATION_PROMPT = PromptTemplate(
 KUZU_EXTRA_INSTRUCTIONS = """
 Instructions:
 
-Generate statement with Kùzu Cypher dialect (rather than standard):
-1. do not use `WHERE EXISTS` clause to check the existence of a property because Kùzu database has a fixed schema.
-2. do not omit relationship pattern. Always use `()-[]->()` instead of `()->()`.
-3. do not include any notes or comments even if the statement does not produce the expected result.
+Generate the Kùzu dialect of Cypher with the following rules in mind:
+
+1. Do not use a `WHERE EXISTS` clause to check the existence of a property.
+2. Do not omit the relationship pattern. Always use `()-[]->()` instead of `()->()`.
+3. Do not include any notes or comments even if the statement does not produce the expected result.
 ```\n"""
 
 KUZU_GENERATION_TEMPLATE = CYPHER_GENERATION_TEMPLATE.replace(