public function updateCMSFields(FieldList $fields)
 {
     if ($this->owner->isInDB()) {
         $fields->fieldByname("Root.Main.Constraints")->push(new Tab("Zones", $zones = new GridField("Zones", "Zones", $this->owner->Zones(), GridFieldConfig_RelationEditor::create()->removeComponentsByType("GridFieldAddNewButton")->removeComponentsByType("GridFieldEditButton"))));
     }
 }