valueToString method
Implementation
@override
String valueToString(Map x) {
final values = _fields.map((entry) => x[entry.key]).toList();
final fields = zipWith<MapEntry, dynamic, String>(
_fields,
values,
(entry, d) => '${entry.key}=${entry.value.valueToString(d)}',
);
return "record {${fields.join('; ')}}";
}