input: Write a function to implement the insertion sort algorithm in Python. If the input list is empty, return an empty 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([5, 3, 8, 6, 7, 2])==[2, 3, 5, 6, 7, 8]
  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([])==[]
output: def insertion_sort(list):
      if not list:
          return []
      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