public function getNavigation(string $elementId): Navigation
    {
        if (!isset($this->navigations[$elementId])) {
            $element = ContentModel::findByPk($elementId);
            Assertion::isInstanceOf($element, ContentModel::class);
            Assertion::eq($element->type, 'bs_tab_start');

            $this->navigations[$elementId] = Navigation::fromSerialized((string) $element->bs_tabs, $elementId);
        }

        return $this->navigations[$elementId];
    }