build method
Implementation
Contract build() {
final validUntil = DateTime.now().add(Duration(minutes: 5));
final ledgerTransferRequests = tx.CreateLedgerTransfers()
..validUntil = Int64(validUntil.microsecondsSinceEpoch);
ledgerTransferRequests.transfers
..clear()
..addAll(_transfers);
return Contract()..transactions = ledgerTransferRequests.writeToBuffer();
}