如何编写解析此JSON的Dart模型类？

dependencies:
  json_annotation: ^4.0.0
  json_serializable: ^4.1.0

import 'package:json_annotation/json_annotation.dart';

part 'model.g.dart';

@JsonSerializable()
class MyModel {
  final String name;
  final int age;

  MyModel(this.name, this.age);

  factory MyModel.fromJson(Map<String, dynamic> json) => _$MyModelFromJson(json);
  Map<String, dynamic> toJson() => _$MyModelToJson(this);
}

flutter pub run build_runner build

import 'dart:convert';

void main() {
  String jsonStr = '{"name": "John", "age": 25}';
  Map<String, dynamic> json = jsonDecode(jsonStr);
  MyModel model = MyModel.fromJson(json);
  print(model.name); // 输出：John
  print(model.age); // 输出：25
}