code: func (s *session) Close() {
  	if s.statsCollector != nil {
  		s.statsCollector.Delete()
  	}
  	ctx := context.TODO()
  	s.RollbackTxn(ctx)
  	if s.sessionVars != nil {
  		s.sessionVars.WithdrawAllPreparedStmt()
  	}
  }
docs: // Close function does some clean work when session end.