code: func (c *MemoryGroupService) GroupContainsMember(ctx context.Context, groupName, uid string) (bool, error) {
  	memoryGroupsMu.Lock()
  	defer memoryGroupsMu.Unlock()
  
  	mg, ok := memoryGroups[groupName]
  	if !ok {
  		return false, constants.ErrGroupNotFound
  	}
  
  	_, contains := elementIndex(mg.Uids, uid)
  	return contains, nil
  }
docs: // GroupContainsMember check whether an UID is contained in given group or not