code: def test_mask_to_bbox_cpu(self):
      self.check(self.mask, self.expected)
  
file_path: chainercv/tests/utils_tests/mask_tests/test_mask_to_bbox.py
imports: from __future__ import division
  import unittest
  import numpy
  from chainer.backends import cuda
  from chainer import testing
  from chainer.testing import attr
  from chainercv.utils import mask_to_bbox
label_desc: Use image node_id 2 for calling the TestMaskToBbox obj's underlying member method code with example usage: obj.test_mask_to_bbox_cpu() without return types