input: def printArrayReverse(arr: List[int]) -> None: 
      """ Prints all elements of a given list in reverse order.
      >>> arr = [1, 2, 3, 4, 5]
      >>> printArrayReverse(arr)
      5 4 3 2 1
      """
      for i in range(len(arr) - 1, -1, -1): 
          print(arr[i], end = " ")
output:     print()