code: func (s *invocationIDSet) Add(c context.Context, ids []int64) error {
  	items := make([]dsset.Item, len(ids))
  	for i, id := range ids {
  		items[i].ID = fmt.Sprintf("%d", id)
  	}
  	return s.Set.Add(c, items)
  }
docs: // Add adds a bunch of invocation IDs to the set.