code: public function getPossibleRoles()
      {
          $roles = [];
          foreach (Yii::$app->collectors['roles']->getAll() as $roleItem) {
              $test = true;
              switch ($roleItem->systemId) {
                  case 'owner':
                      $test = $this->isOwnable;
                  break;
              }
              if ($test) {
                  $roles[] = $roleItem->object->primaryKey;
              }
          }
  
          return $roles;
      }
docs: Get possible roles.
  
  @return [[@doctodo return_type:getPossibleRoles]] [[@doctodo return_description:getPossibleRoles]]