input: def insertion_sort(list: List[int]) -> List[int]:
      """Implement an insertion sort algorithm in Python.
      >>> insertion_sort([3, 1, 4, 2, 5])
      [1, 2, 3, 4, 5]
      >>> insertion_sort([9, 7, 5, 3, 1])
      [1, 3, 5, 7, 9]
      >>> insertion_sort([1, 2, 3, 4, 5])
      [1, 2, 3, 4, 5]
      """
output:     for i in range(1, len(list)):
          key = list[i]
          j = i - 1
          while j >= 0 and key < list[j]:
              list[j + 1] = list[j]
              j -= 1
          list[j + 1] = key
      return list