code: public SortedMap<String, byte[]> annotations()
  	{
  		SortedMap<String,byte[]> ann = new TreeMap<String, byte[]>();
  		if(correlation_id!=null) {
  			long hi = correlation_id.getMostSignificantBits();
  			long lo = correlation_id.getLeastSignificantBits();
  			ann.put("CORR", ByteBuffer.allocate(16).putLong(hi).putLong(lo).array());
  		}
  		return ann;
  	}
docs: Returns a sorted map with annotations to be sent with each message.
  Default behavior is to include the current correlation id (if it is set).