code: func (h *portForwardProxy) requestID(stream httpstream.Stream) (string, error) {
  	requestID := stream.Headers().Get(PortForwardRequestIDHeader)
  	if len(requestID) == 0 {
  		return "", trace.BadParameter("port forwarding is not supported")
  	}
  	return requestID, nil
  }
docs: // requestID returns the request id for stream.