code: def test_forward_gpu(self):
      self.link.to_gpu()
      self._check_forward(
          list(map(chainer.backends.cuda.to_gpu, self.xs))
      )
  
file_path: chainercv/tests/links_tests/model_tests/ssd_tests/test_multibox.py
imports: import numpy
  import unittest
  import chainer
  from chainer import testing
  from chainer.testing import attr
  from chainercv.links.model.ssd import Multibox
label_desc: Use image node_id 4 for calling the TestMultibox obj's underlying member method code with example usage: obj.test_forward_gpu() without return types