input: def insertion_sort(arr):
      """Sorts a list of n distinct integers using the insertion sort algorithm.
      >>> insertion_sort([12, 11, 13, 5, 6])
      [5, 6, 11, 12, 13]
      >>> insertion_sort([31, 41, 59, 26, 41, 58])
      [26, 31, 41, 41, 58, 59]
      """
output:     for i in range(1, len(arr)):
          key = arr[i]
          j = i - 1
          while j >= 0 and key < arr[j]:
              arr[j + 1] = arr[j]
              j -= 1
          arr[j + 1] = key
      return arr