input: Write a python function to return a list with unique items from the input list.
  assert unique_items([1, 2, 2, 3, 4, 4, 5])==[1, 2, 3, 4, 5]
  assert unique_items([10, 20, 20, 30, 40, 40, 50])==[10, 20, 30, 40, 50]
  assert unique_items([5, 5, 5, 5, 5, 5])==[5]
output: def unique_items(lst):
      return list(set(lst))