code: def _clone(self, *args, **kwargs):
          
          clone = super(VersionedQuerySet, self)._clone(**kwargs)
          clone.querytime = self.querytime
          return clone
docs: Overrides the QuerySet._clone method by adding the cloning of the
          VersionedQuerySet's query_time parameter
  
          :param kwargs: Same as the original QuerySet._clone params
          :return: Just as QuerySet._clone, this method returns a clone of the
              original object