protected function processCategoryNode(array $xmlArray)
    {
        $category = [];
        $categoryItem = $xmlArray[Resources::CATEGORY];

        if (is_array($categoryItem)) {
            /** @var SimpleXMLElement $categoryXmlInstance */
            foreach ($xmlArray[Resources::CATEGORY] as $categoryXmlInstance) {
                $categoryInstance = new Category();
                $categoryInstance->parseXml($categoryXmlInstance->asXML());
                $category[] = $categoryInstance;
            }
        } else {
            $categoryInstance = new Category();
            $categoryInstance->parseXml($categoryItem->asXML());
            $category[] = $categoryInstance;
        }

        return $category;
    }