code: def _check(self, dataset, expected_keys):
      self.assertIsInstance(dataset, SliceableDataset)
      self.assertEqual(len(dataset), len(self.dataset))
      self.assertEqual(dataset.keys, expected_keys)
      self.assertEqual(dataset[3], self.expected_sample)
  
file_path: chainercv/tests/chainer_experimental_tests/datasets_tests/sliceable_tests/test_transform_dataset.py
imports: import unittest
  from chainercv.chainer_experimental.datasets.sliceable import SliceableDataset
  from chainercv.chainer_experimental.datasets.sliceable import TransformDataset
  from chainercv.utils import testing
label_desc: Use image node_id 2 for calling the TestTransformDataset obj's underlying member method code with example usage: obj._check(dataset, expected_keys) without return types