code: func New(directory string) blockledger.Factory {
  	return &fileLedgerFactory{
  		blkstorageProvider: fsblkstorage.NewProvider(
  			fsblkstorage.NewConf(directory, -1),
  			&blkstorage.IndexConfig{
  				AttrsToIndex: []blkstorage.IndexableAttr{blkstorage.IndexableAttrBlockNum}},
  		),
  		ledgers: make(map[string]blockledger.ReadWriter),
  	}
  }
docs: // New creates a new ledger factory