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
  
  """
  Implement an insertion sort algorithm in Python.
  >>> insertion_sort([5, 2, 4, 6, 1, 3])
  [1, 2, 3, 4, 5, 6]
  >>> insertion_sort([10, 9, 8, 7, 6])
  [6, 7, 8, 9, 10]
  """
  
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