code: def test_call_gpu(self):
      self.model.to_gpu()
      self.check_call(
          self.model,
          cuda.to_gpu(self.imgs),
          self.bboxes,
          self.labels,
          self.scales,
      )
  
imports: import numpy
  import unittest
  import chainer
  from chainer.backends import cuda
  from chainer import testing
  from chainer.testing import attr
  from chainercv.links import LightHeadRCNNResNet101
  from chainercv.links.model.light_head_rcnn import LightHeadRCNNTrainChain
  from chainercv.utils import generate_random_bbox
label_desc: Use image node_id 4 for calling the TestLightHeadRCNNResNet101Loss obj's underlying member method code with example usage: obj.test_call_gpu() without return types