code: def setUp(self):
      self.ps = numpy.array([5, 3, 4, 1, 2], dtype=numpy.int32)
      self.sampler = utils.WalkerAlias(self.ps)
  
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 1 for calling the TestWalkerAlias obj's underlying member method code with example usage: obj.setUp() without return types