Even if we transform data as ```php transform($data){ return ['id' => $data['id']]; } ``` the response will contain empty attributes object and link object with self-link like ```js "data" : { "type": "users" , "id": "55" , "attributes": { } , "links": { "self": "http://127.0.0.1:80/users/55" } } ``` There is no way to receive a simple response for request like /articles/1/relationships/author r like in examples https://jsonapi.org/format/#fetching-relationships ```js "data" : {"type": "users" , "id": "55" } ```