code: func (m *Mount) Source(podRoot string) string {
  	switch m.Volume.Kind {
  	case "host":
  		return m.Volume.Source
  	case "empty":
  		return filepath.Join(common.SharedVolumesPath(podRoot), m.Volume.Name.String())
  	}
  	return "" // We validate in GenerateMounts that it's valid
  }
docs: // Source computes the real volume source for a volume.
  // Volumes of type 'empty' use a workdir relative to podRoot