code: func (i *Idm) GetID(serial bool) (uint64, error) {
  	if i.handle == nil {
  		return 0, errors.New("ID set is not initialized")
  	}
  	ordinal, err := i.handle.SetAny(serial)
  	return i.start + ordinal, err
  }
docs: // GetID returns the first available id in the set