private function getSortingColumns($sortingDefinition)
    {
        if (null === $sortingDefinition) {
            return [];
        }

        $sortingColumns = [];
        /** @var GroupAndSortingDefinitionInterface $sortingDefinition */
        foreach ($sortingDefinition as $information) {
            /** @var GroupAndSortingInformationInterface $information */
            if ($information->getProperty()) {
                $sortingColumns[] = $information->getProperty();
            }
        }

        return $sortingColumns;
    }