code: public void saveFile(String fileId) {
          URI url = Urls.apiFileStorage(fileId);
          RequestHelper requestHelper = getRequestHelper();
          requestHelper.executeCommand(new HttpPost(url), true);
      }
docs: Marks a file as saved.
  
  This has to be done for all files you want to keep.
  Unsaved files are eventually purged.
  
  @param fileId Resource UUID