input: def insertion_sort(list):
      """
      Implement an insertion sort algorithm in Python.
      >>> insertion_sort([5, 2, 9, 1, 5, 6])
      [1, 2, 5, 5, 6, 9]
      >>> insertion_sort([10, -1, 3, 9, 2, 27, 8, 5, 1, 3])
      [-1, 1, 2, 3, 3, 5, 8, 9, 10, 27]
      """
      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
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