code: func GetStorageNodeAffinityFromAnnotation(annotations map[string]string) (*v1.NodeAffinity, error) {
  	if len(annotations) > 0 && annotations[common.AlphaStorageNodeAffinityAnnotation] != "" {
  		var affinity v1.NodeAffinity
  		err := json.Unmarshal([]byte(annotations[common.AlphaStorageNodeAffinityAnnotation]), &affinity)
  		if err != nil {
  			return nil, err
  		}
  		return &affinity, nil
  	}
  	return nil, nil
  }
docs: // GetStorageNodeAffinityFromAnnotation gets the json serialized data from PersistentVolume.Annotations
  // and converts it to the NodeAffinity type in core.