code: func (a *flexVolumeAttacher) WaitForAttach(spec *volume.Spec, devicePath string, _ *v1.Pod, timeout time.Duration) (string, error) {
  	call := a.plugin.NewDriverCallWithTimeout(waitForAttachCmd, timeout)
  	call.Append(devicePath)
  	call.AppendSpec(spec, a.plugin.host, nil)
  
  	status, err := call.Run()
  	if isCmdNotSupportedErr(err) {
  		return (*attacherDefaults)(a).WaitForAttach(spec, devicePath, timeout)
  	} else if err != nil {
  		return "", err
  	}
  	return status.DevicePath, nil
  }
docs: // WaitForAttach is part of the volume.Attacher interface