code: def check_backward(self, c_grad, h_grad, *inputs):
      gradient_check.check_backward(
          self.link,
          inputs,
          (c_grad, h_grad),
          **self.check_backward_options,
      )
  
imports: import unittest
  import numpy
  import chainer
  from chainer import backend
  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 14 for calling the TestTreeLSTM obj's underlying member method code with example usage: obj.check_backward(c_grad, h_grad) without return types