code: def test_join_length(self):
      dataset_a = dummy_dataset.DummyDataset()
      dataset_b = dummy_dataset.DummyDataset(size=5, keys=("d", "e"))
  
      with self.assertRaises(ValueError):
          dataset_a.join(dataset_b)
  
file_path: chainer/tests/chainer_tests/dataset_tests/tabular_tests/test_join.py
imports: import unittest
  import numpy
  import six
  import chainer
  from chainer import testing
  from chainer_tests.dataset_tests.tabular_tests import dummy_dataset
label_desc: Use image node_id 1 for calling the TestJoinInvalid obj's underlying member method code with example usage: obj.test_join_length() without return types