input: 
  def insertion_sort(list):
      """ Implement an insertion sort algorithm in Python.
      >>> insertion_sort([64, 34, 25, 12, 22, 11, 90])
      [11, 12, 22, 25, 34, 64, 90]
      >>> insertion_sort([5, 2, 9, 1, 5, 6])
      [1, 2, 5, 5, 6, 9]
      """
      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