code: @Override
  	public void declareOutputFields(OutputFieldsDeclarer declarer) {
  		String streamId = getOutputStreamId();
  		Fields names = new Fields(outputFields);
  		logger.info("{} declares {} for stream '{}'",
  				new Object[] {this, names, streamId});
  		declarer.declareStream(streamId, names);
  	}
docs: Registers the {@link #getOutputFields() output field names}.