toJson method
Implementation
String toJson() {
var x = '';
var y = '';
_fields.forEach((element) {
x += ', {';
y = '';
element.forEach((key, value) {
y += ', ${jsonEncode(key)}: ${value.toJsonValue()}';
});
x += y.replaceFirst(', ', '') + '}';
});
x = x.replaceFirst(', ', '');
return '[$x]';
}