langchain/tools/openapi/utils/openapi_utils.py/OpenAPISpec/get_referenced_schema
class OpenAPISpec:    def get_referenced_schema(self, ref: Reference) -> Schema:
        """Get a schema (or nested reference) or err."""
        ref_name = ref.ref.split("/")[-1]
        schemas = self._schemas_strict
        if ref_name not in schemas:
            raise ValueError(f"No schema found for {ref_name}")
        return schemas[ref_name]