Tic-Tac-Toe游戏模式有问题吗？

def check_winner(board):
    # 检查横向
    for row in board:
        if all(cell == 'X' for cell in row) or all(cell == 'O' for cell in row):
            return 'X' if all(cell == 'X' for cell in row) else 'O'
    # 检查纵向
    for col in range(3):
        if all(board[row][col] == 'X' for row in range(3)) or all(board[row][col] == 'O' for row in range(3)):
            return 'X' if all(board[row][col] == 'X' for row in range(3)) else 'O'
    # 检查对角线
    if all(board[i][i] == 'X' for i in range(3)) or all(board[i][i] == 'O' for i in range(3)):
        return 'X' if all(board[i][i] == 'X' for i in range(3)) else 'O'
    if all(board[i][2 - i] == 'X' for i in range(3)) or all(board[i][2 - i] == 'O' for i in range(3)):
        return 'X' if all(board[i][2 - i] == 'X' for i in range(3)) else 'O'
    return None

def is_draw(board):
    return all(cell != '' for row in board for cell in row)