Update base.py

Fix type checking errors by declaring that the schema is a Pydantic BaseModel at this point.

libs/partners/openai/langchain_openai/chat_models/base.py

@@ -1416,10 +1416,11 @@ class AnswerWithJustification(BaseModel):
             strict = strict if strict is not None else True
             response_format = _convert_to_openai_response_format(schema, strict=strict)
             llm = self.bind(response_format=response_format)
+            pydantic_schema = cast(PydanticBaseModel, schema)
             output_parser = (
                 cast(
                     Runnable,
-                    _oai_structured_outputs_parser.with_types(output_type=schema),
+                    _oai_structured_outputs_parser.with_types(output_type=pydantic_schema),
                 )
                 if is_pydantic_schema
                 else JsonOutputParser()