如何使用toJson（）和fromJson（）方法将Json对象映射到dart中的LinkedHashMap？

Question

我需要在Json Object下面将其映射到 LinkedHashMap案例； 我知道这种对象转换，

class CountryInfo {
  String flag;

  CountryInfo({this.flag});

  CountryInfo.fromJson(Map<String, dynamic> json) {
    flag = json['flag'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['flag'] = this.flag;
    return data;
  }
}

我需要了解Timeline.fromJson和toJson（）以下对象，

class Timeline {
  LinkedHashMap<String, int> cases;
}

这是我需要知道的对象。

{
"cases":{
     "4/2/20":151,
     "4/3/20":159,
     "4/4/20":166,
     "4/5/20":176,
     "4/6/20":178,
     "4/7/20":185,
     "4/8/20":189,
     "4/9/20":190,
     "4/10/20":190,
     "4/11/20":198,
     "4/12/20":210,
     "4/13/20":217,
     "4/14/20":233,
     "4/15/20":238,
     "4/16/20":238,
     "4/17/20":244,
     "4/18/20":254,
     "4/19/20":271,
     "4/20/20":304,
     "4/21/20":310,
     "4/22/20":330
    }
}