input: 
  def insertion_sort(list: list) -> list:
      """Sort a list of numbers using the insertion sort algorithm.
      
      >>> insertion_sort([3, 5, 1, 4, 2])
      [1, 2, 3, 4, 5]
      >>> insertion_sort([10, -1, 3, 8, 0])
      [-1, 0, 3, 8, 10]
      >>> insertion_sort([])
      []
      >>> insertion_sort([42, 42, 42, 42])
      [42, 42, 42, 42]
      """
  
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