code: func MountOptionFromSpec(spec *volume.Spec, options ...string) []string {
  	pv := spec.PersistentVolume
  
  	if pv != nil {
  		// Use beta annotation first
  		if mo, ok := pv.Annotations[v1.MountOptionAnnotation]; ok {
  			moList := strings.Split(mo, ",")
  			return JoinMountOptions(moList, options)
  		}
  
  		if len(pv.Spec.MountOptions) > 0 {
  			return JoinMountOptions(pv.Spec.MountOptions, options)
  		}
  	}
  
  	return options
  }
docs: // MountOptionFromSpec extracts and joins mount options from volume spec with supplied options