code: func (db *memDB) ReserveName(name, containerID string) error {
  	return db.withTxn(func(txn *memdb.Txn) error {
  		s, err := txn.First(memdbNamesTable, memdbIDIndex, name)
  		if err != nil {
  			return err
  		}
  		if s != nil {
  			if s.(nameAssociation).containerID != containerID {
  				return ErrNameReserved
  			}
  			return nil
  		}
  		return txn.Insert(memdbNamesTable, nameAssociation{name: name, containerID: containerID})
  	})
  }
docs: // ReserveName registers a container ID to a name
  // ReserveName is idempotent
  // Attempting to reserve a container ID to a name that already exists results in an `ErrNameReserved`
  // A name reservation is globally unique