public function getRootCategory()
    {

        // load the actual store view code
        $storeViewCode = $this->getStoreViewCode($this->getDefaultStoreViewCode());

        // query weather or not we've a root category or not
        if (isset($this->rootCategories[$storeViewCode])) {
            return $this->rootCategories[$storeViewCode];
        }

        // throw an exception if the root category is NOT available
        throw new \Exception(sprintf('Root category for %s is not available', $storeViewCode));
    }