code: def player_marks(grid):
      "Return two results: the player's mark and their opponent's."
      p, q = grid
      return 'XO' if sum(player_bits(p)) == sum(player_bits(q)) else 'OXf player_marks(grid):
      "Return two results: the player's mark and their opponent's."
      p, q = grid
      return 'XO' if sum(player_bits(p)) == sum(player_bits(q)) else 'OX'
docs: Return two results: the player's mark and their opponent's.