code: def for_category(self, category, live_only=False):
          
          filters = {'tag': category.tag}
  
          if live_only:
              filters.update({'entry__live': True})
  
          return self.filter(**filters)
docs: Returns queryset of EntryTag instances for specified category.
  
          :param category: the Category instance.
          :param live_only: flag to include only "live" entries.
          :rtype: django.db.models.query.QuerySet.