public function afterDelete()
 {
     foreach ($this->links as $link) {
         $link->delete();
     }
     parent::afterDelete();
 }
 public function afterDelete()
 {
     //delete events not included in ical file
     $to_delete = CalendarEntry::find()->where(["external_source_id" => $this->id])->all();
     foreach ($to_delete as $event) {
         $event->delete();
     }
     parent::afterDelete();
 }