docs: public Response asynFetch(String url, String bucket, String key, String md5, String etag,
                                String callbackurl, String callbackbody, String callbackbodytype,
                                String callbackhost, int fileType) throws QiniuException {
          String requesturl = configuration.apiHost(auth.accessKey, bucket) + "/sisyphus/fetch";
          StringMap stringMap = new StringMap().put("url", url).put("bucket", bucket).
                  putNotNull("key", key).putNotNull("md5", md5).putNotNull("etag", etag).
                  putNotNull("callbackurl", callbackurl).putNotNull("callbackbody", callbackbody).
                  putNotNull("callbackbodytype", callbackbodytype).
                  putNotNull("callbackhost", callbackhost).putNotNull("file_type", fileType);
          byte[] bodyByte = Json.encode(stringMap).getBytes(Constants.UTF_8);
          return client.post(requesturl, bodyByte,
                  auth.authorizationV2(requesturl, "POST", bodyByte, "application/json"), Client.JsonMime);
      }