code: def test_call_gpu(self):
      self.link.to_gpu()
      self.bboxes.to_gpu()
      self.labels.to_gpu()
      self.imgs.to_gpu()
      self.scale.to_gpu()
      self.check_call()
  
imports: import numpy
  import unittest
  import chainer
  from chainer import testing
  from chainer.testing import attr
  from chainercv.links import FasterRCNNVGG16
  from chainercv.links.model.faster_rcnn import FasterRCNNTrainChain
  from chainercv.utils import generate_random_bbox
label_desc: Use image node_id 4 for calling the TestFasterRCNNVGG16Loss obj's underlying member method code with example usage: obj.test_call_gpu() without return types