code: def _check_example(self, example):
      assert_is_image(example[0])
      self.assertEqual(example[0].shape, self.img_shape)
      assert_is_image(example[2])
      self.assertEqual(example[2].shape, self.img_shape)
  
      self.assertIsInstance(example[1], np.int32)
      self.assertEqual(example[1].ndim, 0)
      self.assertTrue(example[1] >= 0 and example[1] < self.n_class)
      self.assertIsInstance(example[3], np.int32)
      self.assertEqual(example[3].ndim, 0)
      self.assertTrue(example[3] >= 0 and example[1] < self.n_class)
  
file_path: chainercv/tests/datasets_tests/test_siamese_dataset.py
imports: import unittest
  import numpy
  from chainer import testing
  from chainer.datasets import TupleDataset
  from chainercv.datasets import SiameseDataset
  from chainercv.utils.testing.assertions.assert_is_image import assert_is_image
label_desc: Use image node_id 2 for calling the TestSiameseDataset obj's underlying member method code with example usage: obj._check_example(example) without return types