input: 
  def insertion_sort(list):
      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
  
  """
  >>> insertion_sort([4, 3, 2, 1])
  [1, 2, 3, 4]
  >>> insertion_sort([1, 5, 2, 4, 3])
  [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