langchain/tools/openapi/utils/api_models.py/APIProperty/_get_schema
class APIProperty:    def _get_schema(parameter: Parameter, spec: OpenAPISpec) -> Optional[Schema]:
        schema = parameter.param_schema
        if isinstance(schema, Reference):
            schema = spec.get_referenced_schema(schema)
        elif schema is None:
            return None
        elif not isinstance(schema, Schema):
            raise ValueError(f"Error dereferencing schema: {schema}")

        return schema