code: def check_backward(self, x_data, y_grad):
      x = chainer.Variable(x_data)
      y = self.l(x)
      if self.dilate == 1:
          y.grad = y_grad
      elif self.dilate == 2:
          y.grad = y_grad[:, :, 1:-1, 1:-1]
      y.backward()
  
imports: import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  from chainer.functions import relu
  from chainer import testing
  from chainermn import create_communicator
  from chainercv.links.model.mobilenet import TFConv2DBNActiv
  from chainercv.utils.testing import attr
label_desc: Use image node_id 5 for calling the TestTFConv2DBNActiv obj's underlying member method code with example usage: obj.check_backward(x_data, y_grad) without return types