input: def play_game(player1, player2):
      """This function defines the decision-making algorithm for a rock-paper-scissors game.
      It takes two inputs, player1 and player2, which are the choices (rock, paper, or scissors)
      made by the two players. The function then determines the winner based on the rules of the game.
      Examples:
      >>> play_game('rock', 'scissors')
      'Player 1 wins!'
      >>> play_game('paper', 'scissors')
      'Player 2 wins!'
      >>> play_game('rock', 'rock')
      'It is a draw!'
      """
      rules = {'rock': 'scissors', 'scissors': 'paper', 'paper': 'rock'}
      if player1 == player2:
          return 'It is a draw!'
      elif rules[player1] == player2:
          return 'Player 1 wins!'
      elif rules[player2] == player1:
          return 'Player 2 wins!'
output:     else:
          return 'Invalid input!'