code: func (f *FakeVolumeManager) GetVolumesInUse() []v1.UniqueVolumeName {
  	inuse := []v1.UniqueVolumeName{}
  	for v := range f.volumes {
  		inuse = append(inuse, v)
  	}
  	return inuse
  }
docs: // GetVolumesInUse returns a list of the initial volumes