code: def check_retrieval_once(self, names, retrieval_func):
      self.cached_files = [
          os.path.join(self.root, name) for name in names
      ]
      train, test = retrieval_func(
          withlabel=self.withlabel, scale=self.scale
      )
  
      for svhn_dataset in (train, test):
          if self.withlabel:
              self.assertIsInstance(
                  svhn_dataset, tuple_dataset.TupleDataset
              )
              svhn_dataset = svhn_dataset._datasets[0]
          else:
              self.assertIsInstance(svhn_dataset, numpy.ndarray)
  
          self.assertEqual(svhn_dataset.ndim, 4)
          self.assertEqual(svhn_dataset.shape[2], svhn_dataset.shape[3])
  
file_path: chainer/tests/chainer_tests/datasets_tests/test_svhn.py
imports: import os
  import unittest
  import mock
  import numpy
  from chainer.dataset import download
  from chainer.datasets import get_svhn
  from chainer.datasets import tuple_dataset
  from chainer import testing
  from chainer.testing import attr
label_desc: Use image node_id 4 for calling the TestSvhn obj's underlying member method code with example usage: obj.check_retrieval_once(names, retrieval_func) without return types