input: 
  from typing import List
  
  def insertion_sort(arr: List[int]) -> List[int]:
      """
      Sorts a list of 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([-1, -2, -3, -4, -5])
      [-5, -4, -3, -2, -1]
      """
      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 = j - 1
          arr[j + 1] = key
      return arr
  
output:     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 = j - 1
          arr[j + 1] = key
      return arr