input: Write a function to implement a decision-making algorithm for a rock-paper-scissors game using Python. The function should determine the result based on the inputs of two players.
  
  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!'
      elif rules[player2] == player1:
          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!'
      elif rules[player2] == player1:
          return 'Player 2 wins!'