code: def test_call_cpu(self):
      self.check_call(self.x)
  
imports: import unittest
  import mock
  import numpy
  import chainer
  from chainer.backends import cuda
  from chainer import functions
  from chainer import links
  from chainer import testing
  from chainer.testing import attr
label_desc: Use image node_id 4 for calling the TestMLPConvolution2DShapePlaceholder obj's underlying member method code with example usage: obj.test_call_cpu() without return types