public function __construct($baseClass, $relationName, $dataClass)
 {
     parent::__construct($baseClass, $relationName, $dataClass);
     $ids = Session::get($this->itemsSessionKey());
     if (is_null($ids)) {
         return;
     }
     foreach ($ids as $id) {
         $this->add($dataClass::get()->byID($id));
     }
 }
 /**
  * Constructor
  * @param {GridField} $gridField GridField Reference
  */
 public function __construct(GridField $gridField, $baseClass, $relationName, $dataClass)
 {
     $this->gridField = $gridField;
     $this->refreshFromState();
     parent::__construct($baseClass, $relationName, $dataClass);
 }