code: def test_double_backward_no_reduction_cpu(self):
      with chainer.using_config("use_cudnn", "never"):
          self.check_double_backward(
              self.x,
              self.t,
              self.gy,
              self.ggx,
              normalize=self.normalize,
              reduce="no",
          )
  
imports: import math
  import unittest
  import numpy
  import six
  import chainer
  from chainer.backends import cuda
  from chainer import functions
  from chainer import gradient_check
  from chainer import testing
  from chainer.testing import attr
  from chainer import utils
label_desc: Use image node_id 21 for calling the TestSigmoidCrossEntropy obj's underlying member method code with example usage: obj.test_double_backward_no_reduction_cpu() without return types