def load(self, requirements_file=None):
        """Load or reload requirements from a requirements.txt file.

        :param requirements_file: if not given, the filename used from
            initialization will be read again.
        """
        if requirements_file is None:
            requirements_file = self.filename
            if requirements_file is None:
                raise ValueError("no filename provided")
        elif isinstance(requirements_file, text_type):
            requirements_file = Path(requirements_file)
        self.clear()
        with requirements_file.open() as f:
            self.loads(f.read())

        if isinstance(requirements_file, (text_type, Path)):
            self.filename = requirements_file
def get_instance(
        self,
    ) -> Callable[[appengine.GetInstanceRequest], instance.Instance]:
        r"""Return a callable for the get instance method over gRPC.

        Gets instance information.

        Returns:
            Callable[[~.GetInstanceRequest],
                    ~.Instance]:
                A function that, when called, will call the underlying RPC
                on the server.
        """
        # Generate a "stub function" on-the-fly which will actually make
        # the request.
        # gRPC handles serialization and deserialization, so we just need
        # to pass in the functions for each.
        if "get_instance" not in self._stubs:
            self._stubs["get_instance"] = self.grpc_channel.unary_unary(
                "/google.appengine.v1.Instances/GetInstance",
                request_serializer=appengine.GetInstanceRequest.serialize,
                response_deserializer=instance.Instance.deserialize,
            )
        return self._stubs["get_instance"]