code: def test_forward_gpu(self):
      self.check_forward(
          cuda.to_gpu(self.x),
          cuda.to_gpu(self.offset),
          cuda.to_gpu(self.W),
          cuda.to_gpu(self.b),
          self.stride,
          self.pad,
      )
  
imports: import unittest
  import numpy
  import chainer
  from chainer import cuda
  from chainer.functions import convolution_2d
  from chainer.functions import deformable_convolution_2d_sampler
  from chainer import utils
  from chainer import testing
  from chainer.testing import attr
label_desc: Use image node_id 4 for calling the TestDeformableConvolution2DSamplerFunctionLeftBottomOffset obj's underlying member method code with example usage: obj.test_forward_gpu() without return types