code: func (p *Provider) GetQueryExecutorForLedger(cid string) (ledger.QueryExecutor, error) {
  	l := p.Peer.GetLedger(cid)
  	if l == nil {
  		return nil, fmt.Errorf("Could not retrieve ledger for channel %s", cid)
  	}
  
  	return l.NewQueryExecutor()
  }
docs: // GetQueryExecutorForLedger returns a query executor for the specified channel