code: def setUpClass(cls):
      cls.backend = "openslide"
  
file_path: MONAI/tests/test_patch_wsi_dataset.py
imports: from __future__ import annotations
  import os
  import unittest
  from unittest import skipUnless
  import numpy
  from numpy.testing import assert_array_equal
  from parameterized import parameterized
  from monai.data import PatchWSIDataset
  from monai.data.wsi_reader import CuCIMWSIReader, OpenSlideWSIReader
  from monai.utils import optional_import
  from monai.utils.enums import WSIPatchKeys
  from tests.utils import download_url_or_skip_test, testing_data_config
label_desc: Use image node_id 1 for calling the TestPatchWSIDatasetOpenSlide obj's underlying member method code with example usage: obj.setUpClass(cls) without return types