code: func (s *SupportImpl) GetHistoryQueryExecutor(ledgername string) (ledger.HistoryQueryExecutor, error) {
  	lgr := s.Peer.GetLedger(ledgername)
  	if lgr == nil {
  		return nil, errors.Errorf("Channel does not exist: %s", ledgername)
  	}
  	return lgr.NewHistoryQueryExecutor()
  }
docs: // GetHistoryQueryExecutor gives handle to a history query executor for the
  // specified ledger