code: function linkStreams(result, message, erroringStream) {
    result.data = stream.transformPair(message.packets.stream, async (readable, writable) => {
      await stream.pipe(result.data, writable, {
        preventClose: true
      });
      const writer = stream.getWriter(writable);
      try {
        // Forward errors in erroringStream (defaulting to the message stream) to result.data.
        await stream.readToEnd(erroringStream || readable, arr => arr);
        await writer.close();
      } catch(e) {
        await writer.abort(e);
      }
    });
  }
docs: Link result.data to the message stream for cancellation.
  Also, forward errors in the message to result.data.
  @param  {Object} result                  the data to convert
  @param  {Message} message                message object
  @param  {ReadableStream} erroringStream  (optional) stream which either errors or gets closed without data
  @returns {Object}