code: func (mem *Memory) Update(key string, rls *rspb.Release) error {
  	defer unlock(mem.wlock())
  
  	if rs, ok := mem.cache[rls.Name]; ok && rs.Exists(key) {
  		rs.Replace(key, newRecord(key, rls))
  		return nil
  	}
  	return storageerrors.ErrReleaseNotFound(rls.Name)
  }
docs: // Update updates a release or returns ErrReleaseNotFound.