code: def test_length_manual(self):
      dataset = SiameseDataset(
          self.dataset_0, self.dataset_1, length=100
      )
      self.assertEqual(len(dataset), 100)
  
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 7 for calling the TestSiameseDataset obj's underlying member method code with example usage: obj.test_length_manual() without return types