code: def save_optimizer_states(self, fname):
          
          assert self.optimizer_initialized
  
          if self._update_on_kvstore:
              self._kvstore.save_optimizer_states(fname)
          else:
              with open(fname, 'wb') as fout:
                  fout.write(self._updater.get_states())
docs: Saves optimizer (updater) state to a file.
  
          Parameters
          ----------
          fname : str
              Path to output states file.