docs: def _load_fallback_states(self, pg):
          """
          Load the last N deprioritized states will be extracted from the "deprioritized" stash and put to "active" stash.
          N is controlled by 'num_fallback_states'.
  
          :param SimulationManager pg: The simulation manager.
          :return: None
          """
  
          # take back some of the deprioritized states
          l.debug("No more active states. Load some deprioritized states to 'active' stash.")
          if 'deprioritized' in pg.stashes and pg.deprioritized:
              pg.active.extend(pg.deprioritized[-self._num_fallback_states : ])
              pg.stashes['deprioritized'] = pg.deprioritized[ : -self._num_fallback_states]