obsMap<K, V>  method 
Create and auto-track a reactive map - PREVENTS MEMORY LEAKS
Implementation
RxMap<K, V> obsMap<K, V>([Map<K, V>? initialValue]) {
  if (_disposed) {
    throw StateError('Cannot create reactive map on disposed controller');
  }
  final rxMap = RxMap<K, V>(initialValue ?? <K, V>{});
  _trackReactiveObject(rxMap);
  return rxMap;
}