course-site/app/Repositories/Models/Exam/Topic.php

<?php

namespace App\Repositories\Models\Exam;

use App\Repositories\Models\Model;
use Prettus\Repository\Contracts\Transformable;
use Prettus\Repository\Traits\TransformableTrait;

/**
 * Class Topic.
 *
 * @package namespace App\Repositories\Models\Exam;
 */
class Topic extends Model implements Transformable
{
    use TransformableTrait;

    protected $table = 'exam_topics';

    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $guarded = [];

    protected $casts = [
        'body' => 'array',
        'result' => 'array',
    ];

}