private function clearSiteCaches()
    {
        $obj = Craft::$app->sites;
        $refObject = new \ReflectionObject($obj);
        if ($refObject->hasProperty('_sitesById')) {
            $refProperty1 = $refObject->getProperty('_sitesById');
            $refProperty1->setAccessible(true);
            $refProperty1->setValue($obj, null);
        }
        if ($refObject->hasProperty('_sitesByHandle')) {
            $refProperty2 = $refObject->getProperty('_sitesByHandle');
            $refProperty2->setAccessible(true);
            $refProperty2->setValue($obj, null);
        }
        $obj->init(); // reload sites
    }