code: protected List<String> deleteObjects(List<String> keys) throws IOException {
      List<String> result = new ArrayList<>();
      for (String key : keys) {
        boolean status = deleteObject(key);
        // If key is a directory, it is possible that it was not created through Alluxio and no
        // zero-byte breadcrumb exists
        if (status || key.endsWith(getFolderSuffix())) {
          result.add(key);
        }
      }
      return result;
    }
docs: Internal function to delete a list of keys.
  
  @param keys the list of keys to delete
  @return list of successfully deleted keys