code: def test_cpu(self):
      self._test(-1)
  
imports: import unittest
  import chainer
  from chainer import testing
  from chainer.testing import condition
  import numpy
  import scipy.stats
  from chainerrl import distribution
label_desc: Use image node_id 2 for calling the TestSampleDiscreteActions obj's underlying member method code with example usage: obj.test_cpu() without return types