input: def print_unique(my_list):
      """Print the unique elements of a given list.
      >>> print_unique([1, 2, 2, 3, 4, 4])
      1
      2
      3
      4
      >>> print_unique(['apple', 'banana', 'apple', 'orange'])
      apple
      banana
      orange
      """
output:     unique_elements = set(my_list)
      for element in unique_elements:
          print(element)