langchain/tools/openapi/utils/openapi_utils.py/OpenAPISpec/from_file
class OpenAPISpec:    def from_file(cls, path: Union[str, Path]) -> "OpenAPISpec":
        """Get an OpenAPI spec from a file path."""
        path_ = path if isinstance(path, Path) else Path(path)
        if not path_.exists():
            raise FileNotFoundError(f"{path} does not exist")
        with path_.open("r") as f:
            return cls.from_text(f.read())