input: Write a function to simulate a rock-paper-scissors game. The function should take two inputs: the choices of Player 1 and Player 2. Based on the defined rules, the function should determine the winner or if it is a draw. The function should return a string indicating the result of the game.
  
  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('rock', 'paper')=='Player 2 wins!'
  assert play_game('scissors', 'paper')=='Player 1 wins!'
output: def play_game(player1, player2):
      if player1 == player2:
          return 'It is a draw!'
      elif (player1 == 'rock' and player2 == 'scissors') or (player1 == 'scissors' and player2 == 'paper') or (player1 == 'paper' and player2 == 'rock'):
          return 'Player 1 wins!'
      else:
          return 'Player 2 wins!'