toMap method Null safety

Implementation

@override
Map<String, Object?> toMap() {
  return {
    'keyword': this.keyword,
    'tags': this.tags?.map((e) => e).toList(),
    'city': this.city,
    'isCityLimit': this.isCityLimit,
    'scope': this.scope?.index,
    'filter': this.filter?.toMap(),
    'pageIndex': this.pageIndex,
    'pageSize': this.pageSize,
    'extensionsAdcode': this.extensionsAdcode,
  };
}