code: def check_type(self, y_data, z_data, gloss_data):
      y = chainer.Variable(y_data)
      z = chainer.Variable(z_data)
      loss = functions.cross_covariance(y, z, self.reduce)
      loss.grad = gloss_data
      loss.backward()
      self.assertEqual(y_data.dtype, y.grad.dtype)
      self.assertEqual(z_data.dtype, z.grad.dtype)
  
imports: 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 TestCrossCovariance obj's underlying member method code with example usage: obj.check_type(y_data, z_data, gloss_data) without return types