Loads the optimizer (updater) state from the file.

        Parameters
        ----------
        fname : str
            Path to input states file.

def load_optimizer_states(self, fname):
        """Loads the optimizer (updater) state from the file.

        Parameters
        ----------
        fname : str
            Path to input states file.
        """
        assert self._updater is not None, "Cannot load states for distributed training"
        self._updater.set_states(open(fname, 'rb').read())