Why result of rest api mapping is null?

Here is my controller code, why is data returning as a null value?

Future<List<GetEntityKindsModel>> getEntityKinds() async
{
  List<GetEntityKindsModel> data = [];
 try
     {
      dynamic response = await http.get(Uri.parse(url));
      dynamic jsonData = jsonDecode(response.body);
      data = jsonData.map((item)=>GetEntityKindsModel.fromJson(item));
      print('Data -- $data');
     }
     catch(e)
  {
    print('Error -- $e');
  }
  return data;
}

I tried typecasting both jsonData and data into list format but still data returned as null. Is there any issue my with mapping of model to controller? Model has 2 nested classes

    class GetEntityKindsModel {
  GetEntityKindsModel({
    required this.name,
    required this.type,
    required this.classType,
    required this.label,
    required this.pluralLabel,
    this.sharedVisibility,
    this.subscribe,
    required this.id,
    this.entityName,
    required this.parentEntityId,
    required this.languageId,
    this.timestamp,
    this.tagText,
    required this.entityIndex,
    this.code,
    this.blobKey,
  });

  String name;
  Type type;
  ClassType classType;
  String label;
  String pluralLabel;
  String? sharedVisibility;
  Subscribe? subscribe;
  int id;
  String? entityName;
  int parentEntityId;
  LanguageId languageId;
  int? timestamp;
  String? tagText;
  List<String> entityIndex;
  Code? code;
  BlobKey? blobKey;

  factory GetEntityKindsModel.fromJson(Map<String, dynamic> json) => GetEntityKindsModel(
    name: json["name"],
    type: typeValues.map[json["type"]]!,
    classType: classTypeValues.map[json["classType"]]!,
    label: json["label"],
    pluralLabel: json["pluralLabel"],
    sharedVisibility: json["sharedVisibility"],
    subscribe: subscribeValues.map[json["subscribe"]]!,
    id: json["id"],
    entityName: json["entityName"],
    parentEntityId: json["parentEntityId"],
    languageId: languageIdValues.map[json["languageId"]]!,
    timestamp: json["timestamp"],
    tagText: json["tagText"],
    entityIndex: List<String>.from(json["entityIndex"].map((x) => x)),
    code: json["code"] == null ? null : Code.fromJson(json["code"]),
    blobKey: json["blobKey"] == null ? null : BlobKey.fromJson(json["blobKey"]),
  );

  Map<String, dynamic> toJson() => {
    "name": name,
    "type": typeValues.reverse[type],
    "classType": classTypeValues.reverse[classType],
    "label": label,
    "pluralLabel": pluralLabel,
    "sharedVisibility": sharedVisibility,
    "subscribe": subscribeValues.reverse[subscribe],
    "id": id,
    "entityName": entityName,
    "parentEntityId": parentEntityId,
    "languageId": languageIdValues.reverse[languageId],
    "timestamp": timestamp,
    "tagText": tagText,
    "entityIndex": List<dynamic>.from(entityIndex.map((x) => x)),
    "code": code?.toJson(),
    "blobKey": blobKey?.toJson(),
  };
}

class BlobKey {
  BlobKey({
    required this.blobKey,
  });

  String blobKey;

  factory BlobKey.fromJson(Map<String, dynamic> json) => BlobKey(
    blobKey: json["blobKey"],
  );

  Map<String, dynamic> toJson() => {
    "blobKey": blobKey,
  };
}

enum ClassType { STATIC, NULL, DYNAMIC }

final classTypeValues = EnumValues({
  "dynamic": ClassType.DYNAMIC,
  "null": ClassType.NULL,
  "static": ClassType.STATIC
});

class Code {
  Code({
    required this.value,
  });

  String value;

  factory Code.fromJson(Map<String, dynamic> json) => Code(
    value: json["value"],
  );

  Map<String, dynamic> toJson() => {
    "value": value,
  };
}

enum LanguageId { EN_US }

final languageIdValues = EnumValues({
  "en_US": LanguageId.EN_US
});

enum Subscribe { YES, EMPTY }

final subscribeValues = EnumValues({
  "": Subscribe.EMPTY,
  "yes": Subscribe.YES
});

enum Type { PRIMARY, RELATED }

final typeValues = EnumValues({
  "PRIMARY": Type.PRIMARY,
  "RELATED": Type.RELATED
});

class EnumValues<T> {
  Map<String, T> map;
  late Map<T, String> reverseMap;

  EnumValues(this.map);

  Map<T, String> get reverse {
    reverseMap = map.map((k, v) => MapEntry(v, k));
    return reverseMap;
  }
}

Screenshot of print statement

Model class has been made from app.quicktype.io based on the json response of the api, which is too long so can't post here.

The error you are getting is

Error -- Null check operator used on a null value

It would have been useful if you mentioned that before..

It simply means that you are using ! on variable that is null. In your code there is 4 places where this can happen:

type: typeValues.map[json["type"]]!,

classType: classTypeValues.map[json["classType"]]!,

subscribe: subscribeValues.map[json["subscribe"]]!,

languageId: languageIdValues.map[json["languageId"]]!,

I'd suggest to remove the ! for all 4 and make the corresponding field nullable, like

  Type? type;
  ClassType? classType;
  Subscribe? subscribe;
  LanguageId? languageId;

Subscribe is already like this.