code: func (tx *txn) Commit(ctx context.Context) error {
  	ok, resp, _, err := tx.kv.Txn(tx.ops, nil)
  	if err != nil {
  		return err
  	} else if !ok {
  		return fmt.Errorf("transaction failed: %v", resp)
  	}
  	return nil
  }
docs: // Commit commits all operations in a transaction to the data store.
  // Commit is atomic - either all operations in the transaction are
  // committed to the data store, or none of them.