input: Write a function to implement a decision-making algorithm for a rock-paper-scissors game in Python. The function should accept two inputs (player1 and player2) which represent the choices of the players. The function should return a string indicating the result of the game. If both players choose the same option, it should return 'It is a draw!'. If player1 wins, it should return 'Player 1 wins!'. If player2 wins, it should return 'Player 2 wins!'.
  
  def play_game(player1, player2):
      #  Define the winning rules
      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', 'rock') == 'Player 2 wins!'
  assert play_game('paper', 'paper') == 'It is a draw!'
  assert play_game('scissors', 'paper') == 'Player 1 wins!'
  assert play_game('rock', 'rock') == 'It is a draw!'
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!'