code: func (detacher *azureDiskDetacher) UnmountDevice(deviceMountPath string) error {
  	err := mount.CleanupMountPoint(deviceMountPath, detacher.plugin.host.GetMounter(detacher.plugin.GetPluginName()), false)
  	if err == nil {
  		klog.V(2).Infof("azureDisk - Device %s was unmounted", deviceMountPath)
  	} else {
  		klog.Warningf("azureDisk - Device %s failed to unmount with error: %s", deviceMountPath, err.Error())
  	}
  	return err
  }
docs: // UnmountDevice unmounts the volume on the node