Relationship issue

Murin

Here my model Chat.js

import Model from 'flarum/Model';
import mixin from 'flarum/utils/mixin';

export default class Chat extends mixin(Model, {
  time: Model.attribute('time', Model.transformDate),
  user: Model.hasOne('user'),
  content: Model.attribute('content'),
}) {}

My serialize

class ChatSerializer extends AbstractSerializer
{
    /**
     * {@inheritdoc}
     */
    protected $type = 'chats';

    /**
     * {@inheritdoc}
     */
    protected function getDefaultAttributes($chat)
    {
        $attributes = [
            'time'              => $this->formatDate($chat->time),
            'content'           => $chat->content,
            // 'user'              => (int) $chat->user_id,
        ];

        return $attributes;
    }
    
    /**
     * @return \Tobscure\JsonApi\Relationship
     */
    protected function user($chat)
    {
        return $this->hasOne($chat, UserSerializer::class);
    }
}

Could you tell me why i didn't have relationships ?

i try to get user from chat and it return false.