code: public final ChannelFuture writeData(int id, int streamId, HttpData data, boolean endStream) {
  
          assert eventLoop().inEventLoop();
  
          if (closed) {
              ReferenceCountUtil.safeRelease(data);
              return newClosedSessionFuture();
          }
  
          return doWriteData(id, streamId, data, endStream);
      }
docs: Writes an {@link HttpData}.