docs: public <T> T prefop(String persistentId, Class<T> retClass) throws QiniuException {
          StringMap params = new StringMap().put("id", persistentId);
          byte[] data = StringUtils.utf8Bytes(params.formString());
          String url = String.format("%s/status/get/prefop", configuration.apiHost());
          Response response = this.client.post(url, data, null, Client.FormMime);
          if (!response.isOK()) {
              throw new QiniuException(response);
          }
          T object = response.jsonToObject(retClass);
          response.close();
          return object;
      }