groupBy method
argFields might be String or List
Implementation
ConjunctionBase groupBy(dynamic argFields) {
if (argFields != null) {
if (argFields is String) {
groupByList.add(' $argFields ');
} else {
for (String? s in argFields as List<String?>) {
if (s!.isNotEmpty) {
groupByList.add(' $s ');
}
}
}
}
return this;
}