code: def test_preprocess_only_after_download(self, tmp_path):
      file = self._make_file(tmp_path, content="_")
  
      def preprocess(path):
          raise AssertionError(
              "`preprocess` was called although the file was already present."
          )
  
      resource = self.DummyResource(
          file_name=file.name,
          preprocess=preprocess,
      )
  
      resource.load(tmp_path)
  
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 12 for calling the TestOnlineResource obj's underlying member method code with example usage: obj.test_preprocess_only_after_download(tmp_path) without return types