generateFields method
Produce instance fields
Implementation
String generateFields(Map<String, dynamic> fields) {
final keys = fields.keys.toList()..sort();
return keys.fold<List<String>>(<String>[], (acc, key) {
final valueType = fields[key].runtimeType.toString();
return acc..add(' final $valueType ${toCamelCase(key)};');
}).join('\n\n');
}