graph_transformers.llm.py create_simple_model not constraining relationships with enums when using OpenAI LLM

[dennisjunior111]

Checked other resources

• I added a very descriptive title to this issue.
• I searched the LangChain documentation with the integrated search.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).

Example Code

from langchain_experimental.graph_transformers.llm import create_simple_model
from langchain_openai import ChatOpenAI


llm = ChatOpenAI(
    temperature=0, 
    model_name="gpt-4o-mini-2024-07-18"
)

schema = create_simple_model(
    node_labels = ["Person", "Organization"],
    rel_types = ["KNOWS", "EMPLOYED_BY"],
    llm_type = llm._llm_type # openai-chat
)

print(schema.schema_json(indent=4))

Error Message and Stack Trace (if applicable)

No response

Description

The _Graph pydantic model generated from create_simple_model (which LLMGraphTransformer uses when allowed nodes and relationships are provided) does not constrain the relationships (source and target types, relationship type), and the node and relationship properties with enums when using ChatOpenAI.

One can see this by outputting the json schema from the _Graph schema and seeing enum missing from all but SimpleNode.type.

The issue is that when calling optional_enum_field throughout create_simple_model the llm_type parameter is not passed in except for when creating node type. Passing it into each call fixes the issue.

{
    "title": "DynamicGraph",
    "description": "Represents a graph document consisting of nodes and relationships.",
    "type": "object",
    "properties": {
        "nodes": {
            "title": "Nodes",
            "description": "List of nodes",
            "type": "array",
            "items": {
                "$ref": "#/definitions/SimpleNode"
            }
        },
        "relationships": {
            "title": "Relationships",
            "description": "List of relationships",
            "type": "array",
            "items": {
                "$ref": "#/definitions/SimpleRelationship"
            }
        }
    },
    "definitions": {
        "SimpleNode": {
            "title": "SimpleNode",
            "type": "object",
            "properties": {
                "id": {
                    "title": "Id",
                    "description": "Name or human-readable unique identifier.",
                    "type": "string"
                },
                "type": {
                    "title": "Type",
                    "description": "The type or label of the node.. Available options are ['Person', 'Organization']",
                    "enum": [
                        "Person",
                        "Organization"
                    ],
                    "type": "string"
                }
            },
            "required": [
                "id",
                "type"
            ]
        },
        "SimpleRelationship": {
            "title": "SimpleRelationship",
            "type": "object",
            "properties": {
                "source_node_id": {
                    "title": "Source Node Id",
                    "description": "Name or human-readable unique identifier of source node",
                    "type": "string"
                },
                "source_node_type": {
                    "title": "Source Node Type",
                    "description": "The type or label of the source node.. Available options are ['Person', 'Organization']",
                    "type": "string"
                },
                "target_node_id": {
                    "title": "Target Node Id",
                    "description": "Name or human-readable unique identifier of target node",
                    "type": "string"
                },
                "target_node_type": {
                    "title": "Target Node Type",
                    "description": "The type or label of the target node.. Available options are ['Person', 'Organization']",
                    "type": "string"
                },
                "type": {
                    "title": "Type",
                    "description": "The type of the relationship.. Available options are ['KNOWS', 'EMPLOYED_BY']",
                    "type": "string"
                }
            },
            "required": [
                "source_node_id",
                "source_node_type",
                "target_node_id",
                "target_node_type",
                "type"
            ]
        }
    }
}

System Info

> pip freeze | grep langchain
langchain==0.2.10
langchain-community==0.2.9
langchain-core==0.2.22
langchain-experimental==0.0.62
langchain-openai==0.1.17
langchain-text-splitters==0.2.2

platform: wsl2 windows
Python 3.10.14