code: func (p *csiPlugin) constructVolSourceSpec(volSpecName, driverName string) *volume.Spec {
  	vol := &api.Volume{
  		Name: volSpecName,
  		VolumeSource: api.VolumeSource{
  			CSI: &api.CSIVolumeSource{
  				Driver: driverName,
  			},
  		},
  	}
  	return volume.NewSpecFromVolume(vol)
  }
docs: // constructVolSourceSpec constructs volume.Spec with CSIVolumeSource