code: def previous(self):
          
          return self.model.state.get_entity(
              self.entity_type, self.entity_id, self._history_index - 1,
              connected=False)
docs: Return a copy of this object as was at its previous state in
          history.
  
          Returns None if this object is new (and therefore has no history).
  
          The returned object is always "disconnected", i.e. does not receive
          live updates.