code: def check_sample(self):
      counts = numpy.zeros(len(self.ps), numpy.float32)
      for _ in range(1000):
          vs = self.sampler.sample((4, 3))
          numpy.add.at(counts, cuda.to_cpu(vs), 1)
      counts /= 1000 * 12
      counts *= sum(self.ps)
      testing.assert_allclose(self.ps, counts, atol=0.1, rtol=0.1)
  
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 2 for calling the TestWalkerAlias obj's underlying member method code with example usage: obj.check_sample() without return types