input: Write a function that implements an insertion sort algorithm to sort a given list. The function should take a list as input and return the sorted list.
  
  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
  
  assert insertion_sort([3, 4, 5, 1, 2]) == [1, 2, 3, 4, 5]
  assert insertion_sort([3, 5, 10, 1, 2]) == [1, 2, 3, 5, 10]
  assert insertion_sort([4, 3, 1, 2]) == [1, 2, 3, 4]
  assert insertion_sort([3, 5, 4, 1, 2]) == [1, 2, 3, 4, 5]
  assert insertion_sort([]) == []
output: 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