input: Write a python function to find the index of an item in a list.
  assert index_of_item(["a", "b", "c"], "b") == 1
  assert index_of_item([1, 2, 3, 4, 5], 3) == 2
  assert index_of_item(["apple", "banana", "cherry"], "cherry") == 2
  assert index_of_item([10, 20, 30, 40], 40) == 3
output: def index_of_item(lst, item):
      return lst.index(item)