input: Write a function to print the unique elements of a given list. The function should iterate through the list, print each element only once, and use a set to keep track of elements that have already been seen.
  
  
  def print_unique(my_list):
      seen = set()
      for x in my_list:
          if x not in seen:
              print(x)
              seen.add(x)
  
  # Test cases
  assert print_unique([1, 2, 2, 3, 4, 4]) == None # Output should be 1 2 3 4
  assert print_unique([5, 5, 5, 5]) == None # Output should be 5
  assert print_unique([10, 20, 30, 40, 50]) == None # Output should be 10 20 30 40 50
  assert print_unique([]) == None # No output
  
output: def print_unique(my_list):
      seen = set()
      for x in my_list:
          if x not in seen:
              print(x)
              seen.add(x)