destroy method
Unsubscribe from this collection and close the event streams Also closes the event stream of each model within this collection.
Implementation
Future<void> destroy() async {
  await client.send("unsubscribe", rid, null);
  await addEventsController.close();
  await removeEventsController.close();
  await addListener.cancel();
  await removeListener.cancel();
  for (var model in models) {
    await model.destroy();
  }
  models.clear();
}