code: protected String format(ChannelHandlerContext ctx, String eventName, Object arg) {
          if (arg instanceof ByteBuf) {
              return formatByteBuf(ctx, eventName, (ByteBuf) arg);
          } else if (arg instanceof ByteBufHolder) {
              return formatByteBufHolder(ctx, eventName, (ByteBufHolder) arg);
          } else {
              return formatSimple(ctx, eventName, arg);
          }
      }
docs: Formats an event and returns the formatted message.
  
  @param eventName the name of the event
  @param arg       the argument of the event