code: def test_preprocess_extract(self, tmp_path):
      files = None
  
      def download_fn(resource, root):
          nonlocal files
          archive, files = self._make_tar(root, name=resource.file_name)
          return archive
  
      resource = self.DummyResource(
          file_name="folder.tar",
          preprocess="extract",
          download_fn=download_fn,
      )
  
      dp = resource.load(tmp_path)
      assert files is not None, "`download_fn()` was never called"
      assert isinstance(dp, FileOpener)
  
      actual = {path: buffer.read().decode() for path, buffer in dp}
      expected = {
          path.replace(
              resource.file_name, resource.file_name.split(".")[0]
          ): content
          for path, content in files.items()
      }
      assert actual == expected
  
imports: import gzip
  import pathlib
  import sys
  import numpy
  import pytest
  import torch
  from datasets_utils import make_fake_flo_file, make_tar
  from torchdata.datapipes.iter import FileOpener, TarArchiveLoader
  from torchvision.datasets._optical_flow import _read_flo
  from torchvision.datasets.utils import _decompress
  from torchvision.prototype.datasets.utils import Dataset, GDriveResource, HttpResource, OnlineResource
  from torchvision.prototype.datasets.utils._internal import fromfile, read_flo
label_desc: Use image node_id 11 for calling the TestOnlineResource obj's underlying member method code with example usage: obj.test_preprocess_extract(tmp_path) and returns: archive