input: def print_reverse_array(arr):
      """ Print out an array backwards.
      >>> print_reverse_array([1, 2, 3, 4, 5])
      5
      4
      3
      2
      1
      >>> print_reverse_array(['a', 'b', 'c'])
      c
      b
      a
      """
output:     for i in range(len(arr)-1, -1, -1):
          print(arr[i])