In aws s3 amplify storage, on flutter platform, When the app restarts, how do I re-retrieve those unfinished tasks' `operation` instances?

Question

I am using aws s3 amplify storage, on flutter platform. I can create a download task and the function returns an operation instance to control the task to pause, resume and cancel. When the app restarts, how do I re-retrieve those unfinished tasks' operation instances and progress blocks? The following is my sample code:

const op = StorageDownloadFileOptions(accessLevel: StorageAccessLevel.private);
final StorageDownloadFileOperation operation = Amplify.Storage.downloadFile(
  key: key,
  localFile: AWSFile.fromPath(savePath),
  options: op,
  onProgress: (progress) {
    _onDownloadProgress(progress, key, savePath, url);
  },
);

The Flutter s3 storage document doesn't have any information about it.