code: def test_forward_cpu(self):
      self.check_forward(self.x, *self.params, gpu=False)
  
imports: import unittest
  import numpy
  from six import moves
  from chainer.backends import cuda
  from chainer import functions
  from chainer import gradient_check
  from chainer import testing
  from chainer.testing import attr
  from chainer.utils.conv import get_conv_outsize
label_desc: Use image node_id 3 for calling the TestIm2ColForward obj's underlying member method code with example usage: obj.test_forward_cpu() without return types