obsSet<T>  method 
Create and auto-track a reactive set - PREVENTS MEMORY LEAKS
Implementation
RxSet<T> obsSet<T>([Set<T>? initialValue]) {
  if (_disposed) {
    throw StateError('Cannot create reactive set on disposed controller');
  }
  final rxSet = RxSet<T>(initialValue ?? <T>{});
  _trackReactiveObject(rxSet);
  return rxSet;
}