code: def _gen_cache_key_for_slice(url_dict, start_int, total_int, authn_subj_list):
      key_url_dict = copy.deepcopy(url_dict)
      key_url_dict['query'].pop('start', None)
      key_url_dict['query'].pop('count', None)
      key_json = d1_common.util.serialize_to_normalized_compact_json(
          {
              'url_dict': key_url_dict,
              'start': start_int,
              'total': total_int,
              'subject': authn_subj_list,
          }
      )
      logging.debug('key_json={}'.format(key_json))
      return hashlib.sha256(key_json.encode('utf-8')).hexdigest()