code: def check_double_backward(self, x_data, axis, y_grad, x_grad_grad):
      def f(x):
          return functions.normalize(x, eps=self.eps, axis=axis)
  
      gradient_check.check_double_backward(
          f,
          x_data,
          y_grad,
          x_grad_grad,
          **self.check_double_backward_options,
      )
  
imports: import functools
  import itertools
  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
label_desc: Use image node_id 8 for calling the TestL2Normalization obj's underlying member method code with example usage: obj.check_double_backward(x_data, axis, y_grad, x_grad_grad) and returns: functions