Как пройти минмакс?

Question

Я пытаюсь реализовать алгоритм minmax для подключения четырех (я уменьшил плату, чтобы было легче видеть). Однако я застрял на обратном переходе по дереву игры. У меня есть дерево игр в списке в порядке DFS вместе с изображением, чтобы было понятнее:

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def DFS(state, depth_limit):
    game_tree = []
    stack = [] 
    game_tree.append(state)
    potential_moves = state.generate_next_states()#get move states                
    for move in potential_moves:
        move_fn = AbstractGameState(snapshot = move.snapshot, 
                                  is_game_over_fn = is_game_over_connectfour,
                                  generate_next_states_fn = next_boards_connectfour,
                                  endgame_score_fn = endgame_score_connectfour_faster) 
        stack.insert(0,move_fn)   
    while stack != []:
        node = stack.pop(0)
        if node not in game_tree:
            game_tree.append(node)
        if node.is_game_over_fn(node.snapshot):
            pass
        elif node.snapshot.count_pieces() < depth_limit:#set the depth limit
            potential_moves = node.generate_next_states()#create next board states
            for move in potential_moves:
                    move_state = AbstractGameState(snapshot = move.snapshot, 
                                  is_game_over_fn = is_game_over_connectfour,
                                  generate_next_states_fn = next_boards_connectfour,
                                  endgame_score_fn = endgame_score_connectfour_faster) 
                    stack.insert(0,move_state)#append to the stack

    return game_tree

BOARD_EMPTY = ConnectFourBoard(board_array =
                                  (  
                                    ( 0,0,0),
                                    ( 0,0,0),
                                    ( 0,0,0 ),
                                    ),
                                  players = ['Luke', 'Leia'],
                                  whose_turn = 'Luke')

state = AbstractGameState(snapshot = BOARD_EMPTY,
                                  is_game_over_fn = is_game_over_connectfour,
                                  generate_next_states_fn = next_boards_connectfour,
                                  endgame_score_fn = endgame_score_connectfour_faster)

game_tree = DFS(state,3)
for board in game_tree:
    print(board)