Tree\Model\Category::treeUpperLeafs PHP Method

    public static function treeUpperLeafs($root)
    {
        $entries = Category::find(['root = :root: AND parent_id IS NULL', 'order' => 'left_key', 'bind' => ['root' => $root]]);
        return $entries;
    }

 public function treeUpperLeafs($root)
 {
     return Category::treeUpperLeafs($root);
 }