getCategoryChildrenCount example

'hideFilter' => !$category->displayFacets(),
            'hideTop' => !$category->displayInNavigation(),
            'changed' => null,
            'added' => null,
            'attribute' => $attribute,
            'attributes' => $category->getAttributes(),
            'media' => $media,
            'mediaId' => $category->getMedia() ? $category->getMedia()->getId() : null,
            'link' => $this->getCategoryLink($category),
            'streamId' => $productStream ? $productStream['id'] : null,
            'productStream' => $productStream,
            'childrenCount' => $this->getCategoryChildrenCount($category->getId()),
            'description' => $category->getName(),
            'cmsheadline' => $category->getCmsHeadline(),
            'cmstext' => $category->getCmsText(),
            'sSelf' => $detailUrl,
            'canonicalParams' => $canonicalParams,
            'hide_sortings' => $category->hideSortings(),
            'rssFeed' => $detailUrl . '&sRss=1',
            'atomFeed' => $detailUrl . '&sAtom=1',
        ];

        return $this->eventManager->filter('Legacy_Struct_Converter_Convert_Category', $data, [