code: def test_mask_to_bbox_gpu(self):
      self.check(cuda.to_gpu(self.mask), cuda.to_gpu(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 3 for calling the TestMaskToBbox obj's underlying member method code with example usage: obj.test_mask_to_bbox_gpu() without return types