input: Write a python function to count distinct items in a list.
  assert distinct_items_in_list([1, 2, 2, 3, 4, 4, 5]) == 5
  assert distinct_items_in_list(['apple', 'banana', 'apple', 'orange']) == 3
  assert distinct_items_in_list([]) == 0
output: def distinct_items_in_list(lst):
      return len(set(lst))