input: Write a python function to simulate a game of Rock, Paper, Scissors and determine the winner.
  assert playRockPaperScissors("rock", "scissors") == "Player 1 has won."
  assert playRockPaperScissors("scissors", "rock") == "Player 2 has won."
  assert playRockPaperScissors("paper", "paper") == "It's a tie."
output: def playRockPaperScissors(player1, player2):
      if player1 == player2:
          return "It's a tie."
      elif (player1 == "rock" and player2 == "scissors") or \
           (player1 == "scissors" and player2 == "paper") or \
           (player1 == "paper" and player2 == "rock"):
          return "Player 1 has won."
      else:
          return "Player 2 has won."