code: def get_top_level_forum_url(self):
          
          return (
              reverse('forum:index') if self.top_level_forum is None else
              reverse(
                  'forum:forum',
                  kwargs={'slug': self.top_level_forum.slug, 'pk': self.kwargs['pk']},
              )
          )
docs: Returns the parent forum from which forums are marked as read.