input: Write a function to determine the winner in a rock-paper-scissors game between two players. The function should take two inputs representing the choices of Player 1 and Player 2. Based on predefined rules, the function should return 'Player 1 wins!', 'Player 2 wins!', or 'It is a draw!' if both players make the same choice.
  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('paper', 'rock')=='Player 1 wins!'
  assert play_game('scissors', 'scissors')=='It is a draw!'
  assert play_game('paper', 'scissors')=='Player 2 wins!'
  assert play_game('rock', 'paper')=='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!'