code: def test_fetch(self):
      def callback(indices, key_indices):
          self.assertIsNone(indices)
          self.assertIsNone(key_indices)
  
      dataset = dummy_dataset.DummyDataset(
          mode=self.mode,
          return_array=self.return_array,
          callback=callback,
      )
      output = dataset.fetch()
  
      if self.mode is tuple:
          expected = tuple(dataset.data)
      elif self.mode is dict:
          expected = dict(zip(("a", "b", "c"), dataset.data))
      elif self.mode is None:
          expected = dataset.data[0]
      np.testing.assert_equal(output, expected)
  
      if self.mode is dict:
          output = output.values()
      elif self.mode is None:
          output = (output,)
      for out in output:
          if self.return_array:
              self.assertIsInstance(out, np.ndarray)
          else:
              self.assertIsInstance(out, list)
  
file_path: chainer/tests/chainer_tests/dataset_tests/tabular_tests/test_tabular_dataset.py
imports: import unittest
  import numpy
  from chainer import testing
  from chainer_tests.dataset_tests.tabular_tests import dummy_dataset
label_desc: Use image node_id 1 for calling the TestTabularDataset obj's underlying member method code with example usage: obj.test_fetch() without return types