code: function verifyExpiration(initialStart) {
      if (initialStart && global.THORIN_SETUP) return;
      if (opt.removeExpired === false) return;
      let now = new Date(),
        Session = storeObj.model(modelName);
      Session.destroy({
        where: {
          expire_at: {
            lte: now
          }
        },
        logging: false
      }).then((count) => {
        if (count > 0) {
          logger.trace(`Removed ${count} expired sessions.`);
        }
      }).catch((e) => {
        logger.warn('Failed to perform session cleanup', e);
        logger.trace(e.message);
      }).finally(() => setTimeout(() => verifyExpiration(), CLEANUP_TIMER));
    }
docs: /* Step two, once every few hours, we delete the expired sessions.