public static function addRelationClass($name, $class)
    {
        $interface = 'Slick\Orm\RelationInterface';
        if (!class_exists($class)) {
            throw new InvalidArgumentException(
                "{$class} class does not exists"
            );
        }

        $rflClass = new ReflectionClass($class);
        if (!$rflClass->implementsInterface($interface)) {
            throw new InvalidArgumentException(
                "{$class} class does not implement '{$interface}' interface"
            );
        }

        static::$_annotations[$name] = $class;
    }