code: def test_gradient(self):
      def output_0(x, y):
          return self.op_class()(x, y)[0]
  
      def output_1(x, y):
          return self.op_class()(x, y)[1]
  
      utt.verify_grad(
          output_0,
          [np.random.rand(5, 4), np.random.rand(5, 4)],
          n_tests=1,
          rng=TestSumDiffOp.rng,
      )
      utt.verify_grad(
          output_1,
          [np.random.rand(5, 4), np.random.rand(5, 4)],
          n_tests=1,
          rng=TestSumDiffOp.rng,
      )
  
imports: from __future__ import absolute_import, print_function, division
  import unittest
  import theano
  import numpy
  from theano.gof import Op, Apply
  from theano import tensor, function, printing
  from theano.tests import unittest_tools
  import theano
  import numpy
  from theano.compile.ops import as_op
label_desc: Use image node_id 3 for calling the TestSumDiffOp obj's underlying member method code with example usage: obj.test_gradient() and returns: self, self