public function cities($country_id, Request $request = null)
    {
        $query = City::with([
                'administrativeArea' => function ($q) use ($country_id) {
                    $q->where('country_id', $country_id);
                }
            ])
            ->with('administrativeArea.country');

        if ($request) {
            $resource = new Collection($query, 'city', $request);
            return $this->respondWithCollection($resource);
        }
        return $query->get();
    }