code: def __str__(self):
      return self.__class__.__name__
  
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 SumDiffOp obj's underlying member method code with example usage: obj.__str__() and returns: self