code: def test_sample_cpu(self):
      assert not self.sampler.use_gpu
      self.check_sample()
  
file_path: chainer/tests/chainer_tests/utils_tests/test_walker_alias.py
imports: import unittest
  import numpy
  from chainer import backend
  from chainer.backends import cuda
  from chainer import testing
  from chainer.testing import attr
  from chainer import utils
label_desc: Use image node_id 3 for calling the TestWalkerAlias obj's underlying member method code with example usage: obj.test_sample_cpu() without return types