koel 代码，关于 controller 层 user () 方法调用的问题

问题：$request->user()方法调用

代码如下：

//controller:
public function store(PlaylistStoreRequest $request)
    {
        /** @var Playlist $playlist */
        $playlist = $request->user()->playlists()->create([
            'name' => $request->name,
            'rules' => $request->rules,
        ]);
}

//PlaylistStoreRequest文件：
class PlaylistStoreRequest extends Request
{
  public function rules(): array
  {
  return [
  'name' => 'required',
  'songs' => 'array',
 ]; }}

 //Request文件：
 class Request extends AbstractRequest
{
}

//AbstractRequest文件：
abstract class AbstractRequest extends FormRequest
{
  public function authorize(): bool
  {
  return true;
 }
  public function rules(): array
  {
  return [];
 }}

 //model层方法：
 class Playlist extends Model
{
  use CanFilterByUser;

  protected $hidden = ['user_id', 'created_at', 'updated_at'];
  protected $guarded = ['id'];
  protected $casts = [
  'user_id' => 'int',
  'rules' => 'array',
 ];  protected $appends = ['is_smart'];

  public function songs(): BelongsToMany
 {  return $this->belongsToMany(Song::class);
 }
  public function user(): BelongsTo
 {  return $this->belongsTo(User::class);
 }
  public function getIsSmartAttribute(): bool
  {
  return (bool) $this->rules;
 }}