input: Write a function to implement a decision-making algorithm for a rock-paper-scissors game. The function should determine the winner based on the choices made by two players. If both players make the same choice, it should return 'It is a draw!'. If Player 1's choice beats Player 2's choice, it should return 'Player 1 wins!'. If Player 2's choice beats Player 1's choice, it should return 'Player 2 wins!'. The choices are 'rock', 'paper', and 'scissors', where rock beats scissors, scissors beat paper, and paper beats rock.
  def play_game(player1, player2):
      rules = {'rock': 'scissors', 'scissors': 'paper', 'paper': 'rock'}
      if player1 == player2:
          return 'It is a draw!'
      elif rules[player1] == player2:
          return 'Player 1 wins!'
      else:
          return 'Player 2 wins!'
  
  assert play_game('rock', 'scissors') == 'Player 1 wins!'
  assert play_game('scissors', 'paper') == 'Player 1 wins!'
  assert play_game('paper', 'rock') == 'Player 1 wins!'
  assert play_game('rock', 'rock') == 'It is a draw!'
  assert play_game('scissors', 'rock') == 'Player 2 wins!'
output: def play_game(player1, player2):
      rules = {'rock': 'scissors', 'scissors': 'paper', 'paper': 'rock'}
      if player1 == player2:
          return 'It is a draw!'
      elif rules[player1] == player2:
          return 'Player 1 wins!'
      else:
          return 'Player 2 wins!'