public function stop($mergeToParent = true)
    {
        $collector = end(static::$_collectors);
        if ($collector !== $this) {
            return false;
        }
        array_pop(static::$_collectors);
        $collected = $this->_driver->stop();
        $this->add($collected);

        $collector = end(static::$_collectors);
        if (!$collector) {
            return true;
        }
        $collector->add($mergeToParent ? $collected : []);
        $collector->_driver->start();
        return true;
    }