code: func (idserv *V1IDService) Get(v1ID, registry string) (layer.DiffID, error) {
  	if idserv.store == nil {
  		return "", errors.New("no v1IDService storage")
  	}
  	if err := v1.ValidateID(v1ID); err != nil {
  		return layer.DiffID(""), err
  	}
  
  	idBytes, err := idserv.store.Get(idserv.namespace(), registry+","+v1ID)
  	if err != nil {
  		return layer.DiffID(""), err
  	}
  	return layer.DiffID(idBytes), nil
  }
docs: // Get finds a layer by its V1 ID.