code: def test_sum_cpu(self):
      x = numpy.array([[1.0, 2.0, 3.0]], self.dtype)
      self.check_sum(x)
  
imports: import copy
  import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  from chainer import gradient_check
  from chainer import links
  from chainer import testing
  from chainer.testing import attr
  from chainer.testing import condition
label_desc: Use image node_id 4 for calling the TestBinaryHierarchicalSoftmax obj's underlying member method code with example usage: obj.test_sum_cpu() without return types