input: 
  def insertion_sort(arr):
      """
      Sort a list of distinct integers using the insertion sort algorithm.
      >>> insertion_sort([4, 3, 2, 10, 12, 1, 5, 6])
      [1, 2, 3, 4, 5, 6, 10, 12]
      >>> insertion_sort([14, 16, 1, 3, 5, 7, 9, 11])
      [1, 3, 5, 7, 9, 11, 14, 16]
      """
      for i in range(1, len(arr)): 
          key = arr[i] 
          j = i-1
          while j >= 0 and key < arr[j]: 
              arr[j + 1] = arr[j] 
              j -= 1
          arr[j + 1] = key
  
output:     return arr