def get_threads(self, querystring, sort='newest_first', exclude_tags=None):
        assert sort in self._sort_orders
        q = self.query(querystring)
        q.set_sort(self._sort_orders[sort])
        if exclude_tags:
            for tag in exclude_tags:
                q.exclude_tag(tag)
        return self.async_(q.search_threads, (lambda a: a.get_thread_id()))