input: Write a function to print the unique elements of a given list.
  def print_unique(my_list):
      seen = set()
      for x in my_list:
          if x not in seen:
              print(x)
              seen.add(x)
  assert print_unique([1, 2, 2, 3, 4, 4, 5]) == None
  assert print_unique([1, 1, 2, 2, 3, 3, 4, 4, 5, 5]) == None
  assert print_unique([]) == None
  assert print_unique([10, 20, 30, 20, 40, 10]) == None
output: def print_unique(my_list):
      seen = set()
      for x in my_list:
          if x not in seen:
              print(x)
              seen.add(x)