public static function nodeChildren($parentId)
    {
        $parentId = intval($parentId);
        if (!static::$caching || empty(static::$_children[$parentId])) {
            $query = static::find()
                ->where(['parent_id' => $parentId])
                ->orderBy(static::$defaultOrderBy);
            $childList = $query
              //->asArray()
                ->all();
            if (static::$caching) {
                static::$_children[$parentId] = $childList;
            } else {
                return $childList;
            }
        }
        return static::$_children[$parentId];
    }