private static function _resolveHasMany($attr, $value)
    {
        $cls = get_called_class();
        if (!self::hasHasMany($attr)) {
            return null;
        }

        $configs       = self::$_has_many[$cls][$attr];
        $has_many_cls  = self::hasManyClass($attr);
        $this_key      = self::hasManyForeignKey($attr);
        $collection    = $has_many_cls::where(array($this_key => $value));
        return $collection;
    }