input: Write a function to print the unique elements of a given list. If the list is empty, it should print nothing.
  assert print_unique([1, 2, 3, 3, 4, 4, 5])==None
  assert print_unique([1, 1, 1, 2, 2, 3])==None
  assert print_unique([])==None
output: def print_unique(lst):
      if lst:
          unique_elements = list(set(lst))
          for element in unique_elements:
              print(element)