Neo4jGraph(enhance_schema=True) Fails with CypherSyntaxError on Boolean Relationship Properties

[Hiraveb]

When initializing langchain_neo4j.graphs.Neo4jGraph with enhance_schema=True, a neo4j.exceptions.CypherSyntaxError: {code: Neo.ClientError.Statement.SyntaxError} {message: Variable RETURN not defined ... "RETURN {} AS output"} occurs. This error appears during the schema introspection process, specifically when the Neo4j graph contains relationships with properties of boolean type.

Steps to Reproduce:

1. Populate a Neo4j database with a graph schema that includes at least one relationship type having a property of boolean type.
   Example: A relationship (:Fabric)-[r:HAS_COLOR]->(:Color) where r has a property IsMasterColor which is set to Cypher true or false.

2.In Python, attempt to initialize Neo4jGraph pointing to this database with enhance_schema=True:

    from langchain_neo4j.graphs import Neo4jGraph

    graph = Neo4jGraph(
        url="bolt://localhost:7687",
        username="neo4j",
        password="your_password",
        enhance_schema=True # Problem occurs with True
    )

3. The initialization fails with the CypherSyntaxError.

File ".../langchain_neo4j/graphs/neo4j_graph.py", line 278, in refresh_schema
    self.structured_schema = get_structured_schema(
                             ^^^^^^^^^^^^^^^^^^^^^^
File ".../neo4j_graphrag/schema.py", line 356, in get_structured_schema
    enhance_schema(
File ".../neo4j_graphrag/schema.py", line 903, in enhance_schema
    enhance_properties(
File ".../neo4j_graphrag/schema.py", line 836, in enhance_properties
    enhanced_info = query_database(
File ".../neo4j_graphrag/schema.py", line 164, in query_database
    data = driver.execute_query(
...
neo4j.exceptions.CypherSyntaxError: {code: Neo.ClientError.Statement.SyntaxError} {message: Variable `RETURN` not defined (line 3, column 1 (offset: 50))
"RETURN {} AS output"
 ^}

• The error does not occur if the boolean property (e.g., IsMasterColor) is removed from the relationships in the database.
• The error does not occur if Neo4jGraph is initialized with enhance_schema=False.
• The boolean property itself is correctly stored and typed as boolean in Neo4j when created.
• The issue seems to stem from how neo4j_graphrag.schema.enhance_properties (or a function it calls) constructs its Cypher queries for schema introspection when encountering boolean relationship properties, leading to the malformed RETURN {} AS output query.

[alexthomas93]

Thanks for raising this @Hiraveb. I've raised a PR in the neo4j-graphrag library which should fix the underlying issue. I'll update the dependency once that fix has been merged and another release of it is published. A fix should be available here in the next release after that.