code: func (ds *dockerService) PortForward(_ context.Context, req *runtimeapi.PortForwardRequest) (*runtimeapi.PortForwardResponse, error) {
  	if ds.streamingServer == nil {
  		return nil, streaming.NewErrorStreamingDisabled("port forward")
  	}
  	_, err := checkContainerStatus(ds.client, req.PodSandboxId)
  	if err != nil {
  		return nil, err
  	}
  	// TODO(tallclair): Verify that ports are exposed.
  	return ds.streamingServer.GetPortForward(req)
  }
docs: // PortForward prepares a streaming endpoint to forward ports from a PodSandbox, and returns the address.