code: def setup_gpu(self):
      self.x1 = cuda.to_gpu(self.x1)
      self.x2 = cuda.to_gpu(self.x2)
      self.y1 = cuda.to_gpu(self.y1)
      self.y2 = cuda.to_gpu(self.y2)
      self.gx1.to_gpu()
      self.gx1_orig.to_gpu()
      self.gx2_orig.to_gpu()
      self.gx1_accum.to_gpu()
      self.gy1 = cuda.to_gpu(self.gy1)
      self.gy2 = cuda.to_gpu(self.gy2)
      self.f.forward_gpu = mock.MagicMock(
          return_value=(self.y1, self.y2)
      )
      self.f._mock_backward = mock.MagicMock(
          return_value=(self.gx1, self.gx2)
      )
  
imports: import unittest
  import mock
  import numpy
  import six
  import chainer
  from chainer import _backprop_utils
  from chainer.backends import cuda
  from chainer import testing
  from chainer.testing import attr
label_desc: Use image node_id 4 for calling the TestFunctionNode obj's underlying member method code with example usage: obj.setup_gpu() without return types