input: Write a function to implement a decision-making algorithm for a rock-paper-scissors game. The function should accept two parameters representing the choices of Player 1 and Player 2. It should determine the winner based on predefined rules and return a string indicating the result. If both players choose the same option, the function should return 'It is a draw!' If Player 1 beats Player 2, it should return 'Player 1 wins!' and vice versa. The function should handle inputs in lowercase.
  
  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('scissors', 'scissors') == 'It is a draw!'
  assert play_game('paper', 'paper') == '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!'