求助，请问怎么使用HarmonyOS的用户首选项模块扩展支持JSON数据存储

type ValueType = string | number | boolean;

class LocalStorage {
   private preference: preferences.Preferences;

   async put(key: string, value: ValueType | object) {
       if (typeof value === 'object') {
           value = JSON.stringify(value);
       }
       await this.preference.put(key, value);
       await this.preference.flush();
   }

   async getValue(key: string): Promise<ValueType> {
       let value = await this.preference.get(key, '') as string;
       if (isJsonObject(value)) {
           value = JSON.parse(value);
       }
       return Promise.resolve(value);
   }
}
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