private function getPrevNext(HasNodeInterface $page, $loop)
 {
     $class = ClassLookup::getClass($page);
     $id = $page->getId();
     if (false === isset($this->nav[$class][$id])) {
         $parent = $this->contentCategory->getParentCategory($page, true);
         $siblings = $this->siteTree->getChildren($parent, ['refName' => $class, 'depth' => 1]) ?: new UnknownNodeBranch();
         $this->nav[$class][$id] = $this->calculatePrevNext($siblings, $page, $loop);
     }
     return array_values($this->nav[$class][$id]);
 }
 public function getParentCategory(HasNodeInterface $page, $includeHidden = false)
 {
     return $this->categoryService->getParentCategory($page, $includeHidden);
 }