code: def test_rpn_loss_gpu(self):
      import cupy
  
      self._check_rpn_loss(cupy)
  
imports: from __future__ import division
  import numpy
  import unittest
  import chainer
  from chainer import testing
  from chainer.testing import attr
  from chainercv.links.model.fpn import RPN
  from chainercv.links.model.fpn import rpn_loss
label_desc: Use image node_id 3 for calling the TestRPNLoss obj's underlying member method code with example usage: obj.test_rpn_loss_gpu() without return types