protected function filterClasses($key, $classes, $internal, $user)
    {
        $ret = [];

        if ($internal) {
            $ret['Internal ' . $key] = \array_filter($classes, function ($class) {
                $refl = new \ReflectionClass($class);

                return $refl->isInternal();
            });
        }

        if ($user) {
            $ret['User ' . $key] = \array_filter($classes, function ($class) {
                $refl = new \ReflectionClass($class);

                return !$refl->isInternal();
            });
        }

        if (!$user && !$internal) {
            $ret[$key] = $classes;
        }

        return $ret;
    }