input: Write a python function to simulate a rock-paper-scissors game and return the result based on user input and random computer input.
  assert rock_paper_scissors(0, 2) == "You win!"
  assert rock_paper_scissors(1, 0) == "You win!"
  assert rock_paper_scissors(2, 1) == "You win!"
  assert rock_paper_scissors(0, 0) == "It's a draw!"
  assert rock_paper_scissors(1, 1) == "It's a draw!"
  assert rock_paper_scissors(2, 2) == "It's a draw!"
  assert rock_paper_scissors(0, 1) == "Computer wins!"
  assert rock_paper_scissors(1, 2) == "Computer wins!"
  assert rock_paper_scissors(2, 0) == "Computer wins!"
output: import random
  
  def rock_paper_scissors(user_choice, computer_choice=None):
      if computer_choice is None:
          computer_choice = random.randint(0, 2)
      
      if user_choice == computer_choice:
          return "It's a draw!"
      elif (user_choice == 0 and computer_choice == 2) or (user_choice == 1 and computer_choice == 0) or (user_choice == 2 and computer_choice == 1):
          return "You win!"
      else:
          return "Computer wins!"