KafkaLog4jAppender is quite useful for us to send our log4j logs to the Kafka system with ease. However, according to our experience, it is not so that convenient to customize the message content before emitting it out. Sometimes, we need to decorate the message like adding more system level information before passing it to the producer. I wonder if it is possible to add one subAppend() function, like org.apache.log4j.WriterAppender does. Thus, the end user can customize their message by overwriting the subAppend() only in their own hierarchy class, and re-use all the rest part.