input: Write a python function to find the index of the smallest integer in a list.
  assert find_smallest_int([1, 4, 7, 8, 10]) == 0
  assert find_smallest_int([10, 20, -5, 0, 3]) == 2
  assert find_smallest_int([5, 7, 9, -8, 6, 4, 3]) == 3
output: def find_smallest_int(lst):
      return lst.index(min(lst))