finalCallback = (err, stats) => {
			if (logger) logger.time("beginIdle");
			this.idle = true;
			this.cache.beginIdle();
			this.idle = true;
			if (logger) logger.timeEnd("beginIdle");
			this.running = false;
			if (err) {
				this.hooks.failed.call(err);
			}
			if (callback !== undefined) callback(err, stats);
			this.hooks.afterDone.call(/** @type {Stats} */ (stats));
		}
@param {Error | null} err error
@param {Stats=} stats stats