code: func (vm *volumeManager) getUnattachedVolumes(expectedVolumes []string) []string {
  	unattachedVolumes := []string{}
  	for _, volume := range expectedVolumes {
  		if !vm.actualStateOfWorld.VolumeExists(v1.UniqueVolumeName(volume)) {
  			unattachedVolumes = append(unattachedVolumes, volume)
  		}
  	}
  	return unattachedVolumes
  }
docs: // getUnattachedVolumes returns a list of the volumes that are expected to be attached but
  // are not currently attached to the node