code: func (session *Session) Rollback() error {
  	if !session.isAutoCommit && !session.isCommitedOrRollbacked {
  		session.saveLastSQL(session.engine.dialect.RollBackStr())
  		session.isCommitedOrRollbacked = true
  		session.isAutoCommit = true
  		return session.tx.Rollback()
  	}
  	return nil
  }
docs: // Rollback When using transaction, you can rollback if any error