groupBy method
Implementation
Map<String, List<T>> groupBy(String fieldName) {
Map<String, List<T>> result = {};
final groups = _harnCollection.groupBy(fieldName);
groups.forEach((key, value) {
Map<String, List<T>> r = {};
r["$key"] = value.map((e) => fromMap(e)).toList();
result.addAll(r);
});
harnLog.register({"groupBy": result});
return result;
}