@Override
 public void writeTo(StreamOutput out) throws IOException {
   super.writeTo(out);
   writeAcknowledged(out);
   if (!isAcknowledged()) {
     error.writeTo(out);
   }
 }
 @Override
 public void readFrom(StreamInput in) throws IOException {
   super.readFrom(in);
   readAcknowledged(in);
   if (!isAcknowledged()) {
     error = new PipelineFactoryError();
     error.readFrom(in);
   }
 }
 @Override
 public void readFrom(StreamInput in) throws IOException {
   super.readFrom(in);
   readAcknowledged(in);
 }