public function has_siblings() {
        if (empty($this->parent) || empty($this->parent->children)) {
            return false;
        }
        if ($this->parent->children instanceof navigation_node_collection) {
            $count = $this->parent->children->count();
        } else {
            $count = count($this->parent->children);
        }
        return ($count > 1);
    }