input: 
  def is_game_won(board: List[List[str]]) -> bool:
      """ Check if a TicTacToe game on the given board has been won by any player.
      The board is represented as a list of lists of strings, where each string is 
      either 'x', 'o', or '_' (empty).
      >>> is_game_won([['x', 'x', 'x'], ['o', '_', 'o'], ['_', 'o', '_']])
      True
      >>> is_game_won([['x', 'o', '_'], ['x', 'o', '_'], ['_', 'o', 'x']])
      False
      """
  
output:     for row in board:
          if row[0] == row[1] == row[2] and row[0] != '_':
              return True
      for col in range(3):
          if board[0][col] == board[1][col] == board[2][col] and board[0][col] != '_':
              return True
      if board[0][0] == board[1][1] == board[2][2] and board[0][0] != '_':
          return True
      if board[0][2] == board[1][1] == board[2][0] and board[0][2] != '_':
          return True
      return False