private function getFirstSorting(GroupAndSortingDefinitionInterface $sortingDefinition = null)
    {
        if (null === $sortingDefinition) {
            return '';
        }

        foreach ($sortingDefinition as $information) {
            /** @var GroupAndSortingInformationInterface $information */
            if ($information->getProperty()) {
                return $information->getProperty();
            }
        }

        return '';
    }