cara membuat kelas model untuk json kompleks di flutter

class Photo{  final String id;  final String title;  final String url;  Photo({    this.id,    this.url,    this.title}) ;  factory Photo.fromJson(Map<String, dynamic> json){    return new Photo(      id: json['id'].toString(),      title: json['title'],      url: json['json'],    );  }}
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