get method
Implementation
Future<XData?> get(field, value) async {
if (fields.where((element) => element.field == field).isEmpty) {
throw Exception('Field $field not found');
}
var dataSet = await _getAllDocs();
return dataSet
.where((element) => element.data[field] == value)
.toList()
.isEmpty
? null
: dataSet.where((element) => element.data[field] == value).toList()[0];
}