code: def test_dafault_bbox(self):
      self.assertEqual(self.coder._default_bbox.shape, (self.n_bbox, 4))
  
file_path: chainercv/tests/links_tests/model_tests/ssd_tests/test_multibox_coder.py
imports: import numpy
  import unittest
  from chainer.backends import cuda
  from chainer import testing
  from chainer.testing import attr
  from chainercv.links.model.ssd import MultiboxCoder
label_desc: Use image node_id 4 for calling the TestMultiboxCoder obj's underlying member method code with example usage: obj.test_dafault_bbox() without return types