code: public function clearCache(string $namespace = null) {
  		if (null !== $namespace) {
  			$this->cacheStore->remove(self::APP_CACHE_PREFIX . $namespace, array());
  			return;
  		}
  		
  		$this->cacheStore->clear();
  	}
docs: If no namespace is provided, the whole dbtext cache is cleared.
  
  @param string $namespace