input: Write a function to implement a decision-making algorithm for a rock-paper-scissors game. The function should take two arguments, player1 and player2, which represent the choices made by two players. The function should return a string indicating the result of the game. If both players make the same choice, it should return 'It is a draw!'. If player1's choice wins over player2's choice, it should return 'Player 1 wins!'. If player2's choice wins over player1's choice, it should return 'Player 2 wins!'.
  assert play_game('rock', 'scissors') == 'Player 1 wins!'
  assert play_game('paper', 'rock') == 'Player 1 wins!'
  assert play_game('scissors', 'paper') == 'Player 1 wins!'
  assert play_game('rock', 'paper') == 'Player 2 wins!'
  assert play_game('scissors', 'rock') == 'Player 2 wins!'
  assert play_game('paper', 'scissors') == 'Player 2 wins!'
  assert play_game('rock', 'rock') == 'It is a draw!'
  assert play_game('paper', 'paper') == 'It is a draw!'
  assert play_game('scissors', 'scissors') == 'It is a draw!'
output: def play_game(player1, player2):
      if player1 == player2:
          return 'It is a draw!'
      elif (player1 == 'rock' and player2 == 'scissors') or (player1 == 'paper' and player2 == 'rock') or (player1 == 'scissors' and player2 == 'paper'):
          return 'Player 1 wins!'
      else:
          return 'Player 2 wins!'