Flarum\Api\Serializer\AbstractSerializer::setActor PHP Method

    public function setActor(User $actor)
    {
        $this->actor = $actor;
    }

 /**
  * Get the result of an API request to show the current user.
  *
  * @return array
  */
 protected function getUserDocument(Request $request)
 {
     $actor = $request->getAttribute('actor');
     $this->userSerializer->setActor($actor);
     $resource = new Resource($actor, $this->userSerializer);
     $document = new Document($resource->with('groups'));
     return $document->toArray();
 }