问是dart中json序列化所必需的tojson和fromjson方法吗？

EN

    class UserData
    {
      int id;
      String email;
      String first_name;
      String last_name;
      String avatar;
    
      UserData({this.id, this.email, this.first_name, this.last_name, this.avatar});
    
      factory UserData.fromJson(Map<String, dynamic> json) => _$UserDataFromJson(json);
    
    
      Map<String, dynamic> toJson() => _$UserDataToJson(this);
    
    }

UserData  _$UserDataFromJson(Map<String, dynamic> json) {
  return UserData(
    id: json['id'] as int,
    email: json['email'] as String,
    first_name: json['first_name'] as String,
    last_name: json['last_name'] as String,
    avatar: json['avatar'] as String,
  );
}

Map<String, dynamic> _$UserDataToJson(UserData instance) => <String, dynamic>{
      'id': instance.id,
      'email': instance.email,
      'first_name': instance.first_name,
      'last_name': instance.last_name,
      'avatar': instance.avatar,
    };