anchor.diff:    void _notifyChange(Symbol prop) {
       notifyChange(new PropertyChangeRecord(prop));
     }
  -
  -  static const _NOTE_SYNC_FORWARD_PROPS = const [const Symbol('isUpdated')];
   }
  
positive.code: 
    Map<String, Note> get _noteStorage => _noteSync.map;
  
    void _onNoteSyncChanged(List<ChangeRecord> records) {
      var forwardProps = records
          .where((ChangeRecord cr) => cr is PropertyChangeRecord)
          .map((pcr) => pcr.field)
          .where((Symbol field) => _NOTE_SYNC_FORWARD_PROPS.contains(field))
          .toList();
  
      for(var matchField in forwardProps) {
        _notifyChange(matchField);
      }
    }
  
    void _updateNotesList() {
  
negative.code:     }
  
      // TODO: hold onto the subscription. Support dispose?
      filterPropertyChangeRecords(_noteSync, const Symbol('isUpdated'))
        .listen(_onNoteSyncIsUpdated);
  
      _updateNotesList();
    }
  