anchor.diff:    void _send(Map data) {
       _log.fine('SEND', jsonEncode(data));
       _process.stdin.writeln(jsonEncode(data));
  -    _process.stdin.flush();
     }
   
     void _pump() async {
       await for (final request in _requests.stream) {
         _send(request.toJson());
   
  -      request.signal?._send.stream.listen((status) {
  +      final signalSubscription = request.signal?._sendStream.listen((status) {
           _send({'kind': 'signal', 'status': status});
         });
   
  
positive.code:     Map<dynamic, dynamic>? params,
      Signaler? signal,
    }) async {
      try {
        return await _rpc.command(
          action,
          devicePath.segments + subPath + target,
  
negative.code:   final _recv = StreamController<Signal>();
  
    Stream<Signal> get signals => _recv.stream;
  
    Stream<String> get _sendStream => _send.stream;
  
    void cancel() {
      _send.add('cancel');
  