input: Write a python function to implement insertion sort.
  assert insertion_sort([4, 1, 3, 6, 2, 5]) == [1, 2, 3, 4, 5, 6]
  assert insertion_sort([10, 7, 8, 5, 3, 2]) == [2, 3, 5, 7, 8, 10]
  assert insertion_sort([1, 0, 0, 1, 0]) == [0, 0, 0, 1, 1]
output: def insertion_sort(arr):
      for i in range(1, arr.length):
          key = arr[i]
          j = i - 1
          while j >= 0 and key < arr[j]:
              arr[j + 1] = arr[j]
              j -= 1
          arr[j + 1] = key
      return arr