input: Write a python function to implement insertion sort for a list of numbers.
  assert InsertionSort().sort([5, 2, 4, 1, 3]) == [1, 2, 3, 4, 5]
  assert InsertionSort().sort([9, 7, 5, 3, 1]) == [1, 3, 5, 7, 9]
  assert InsertionSort().sort([10, 20, 30, 5, 15]) == [5, 10, 15, 20, 30]
output: class InsertionSort:
      def sort(self, lst):
          for i in range(1, len(lst)):
              key = lst[i]
              j = i - 1
              while j >= 0 and key < lst[j]:
                  lst[j + 1] = lst[j]
                  j -= 1
              lst[j + 1] = key
          return lst