code: def iflag_unique_items(list_):
      
      seen = set()
      def unseen(item):
          if item in seen:
              return False
          seen.add(item)
          return True
      flag_iter = (unseen(item) for item in list_)
      return flag_iter
docs: Returns a list of flags corresponding to the first time an item is seen
  
      Args:
          list_ (list): list of items
  
      Returns:
          flag_iter