setIsSubtotal method
Mark a row as a subtotal node (shows +/- expand/collapse button).
Implementation
Future<void> setIsSubtotal(int row, bool isSubtotal) async {
await VolvoxGridService.DefineRows(DefineRowsRequest()
..gridId = _gridId
..rows.add(RowDef()
..index = row
..isSubtotal = isSubtotal));
}