def step_back(self):
        ''' Return to the previous state of the game

        Returns:
            (bool): True if the game steps back successfully
        '''
        if not self.round.trace:
            return False

        #winner_id will be always None no matter step_back from any case
        self.winner_id = None

        #reverse round
        player_id, cards = self.round.step_back(self.players)

        #reverse player
        if (cards != 'pass'):
            self.players[player_id].played_cards = self.round.find_last_played_cards_in_trace(player_id)
        self.players[player_id].play_back()

        #reverse judger.played_cards if needed
        if (cards != 'pass'):
            self.judger.restore_playable_cards(player_id)

        self.state = self.get_state(self.round.current_player)
        return True
 Return to the previous state of the game

        Returns:
            (bool): True if the game steps back successfully
        
rlcard/games/doudizhu/game.py