input: Write a function to implement the insertion sort algorithm in Python. 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([4,3,2,10,12,1,5,6])==[1, 2, 3, 4, 5, 6, 10, 12]
  assert insertion_sort([1,2,3,4,5])==[1, 2, 3, 4, 5]
  assert insertion_sort([5,4,3,2,1])==[1, 2, 3, 4, 5]
  assert insertion_sort([0,0,0,0])==[0, 0, 0, 0]
  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