experimental[patch]: Flatten relationships in LLM graph transformer (#19642)

libs/experimental/langchain_experimental/graph_transformers/llm.py

@@ -112,8 +112,18 @@ def create_simple_model(
     class SimpleRelationship(BaseModel):
         """Represents a directed relationship between two nodes in a graph."""
 
-        source: SimpleNode = Field(description="The source node of the relationship.")
-        target: SimpleNode = Field(description="The target node of the relationship.")
+        source_node_id: str = Field(
+            description="Name or human-readable unique identifier of source node"
+        )
+        source_node_type: str = optional_enum_field(
+            node_labels, description="The type or label of the source node."
+        )
+        target_node_id: str = Field(
+            description="Name or human-readable unique identifier of target node"
+        )
+        target_node_type: str = optional_enum_field(
+            node_labels, description="The type or label of the target node."
+        )
         type: str = optional_enum_field(
             rel_types, description="The type of the relationship.", is_rel=True
         )
@@ -136,8 +146,8 @@ def map_to_base_node(node: Any) -> Node:
 
 def map_to_base_relationship(rel: Any) -> Relationship:
     """Map the SimpleRelationship to the base Relationship."""
-    source = map_to_base_node(rel.source)
-    target = map_to_base_node(rel.target)
+    source = Node(id=rel.source_node_id.title(), type=rel.source_node_type.capitalize())
+    target = Node(id=rel.target_node_id.title(), type=rel.target_node_type.capitalize())
     return Relationship(
         source=source, target=target, type=rel.type.replace(" ", "_").upper()
     )