code: public function purgeInternalCache()
  	{
  		$container = System::getContainer();
  
  		$clearer = $container->get('contao.cache.clear_internal');
  		$clearer->clear($container->getParameter('kernel.cache_dir'));
  
  		// Add a log entry
  		$this->log('Purged the internal cache', __METHOD__, TL_CRON);
  	}
docs: Purge the internal cache