code: protected void writeResponse(final HttpStatus httpStatus, final NextFilter nextFilter,
                                   final IoSession session, final HttpRequestMessage httpRequest) {
          writeResponse(httpStatus, null, nextFilter, session, httpRequest);
      }
docs: Write a response back to the client (downstream) with a particular Http Status code.
  
  @param httpStatus the http status to write onto the response
  @param nextFilter the next filter to write the reply to
  @param session    the client session
  @param httpRequest the originating http request