code: def test_grad_duplicate_input(self):
      # test that the grad works when a variable
      # appears in more than one place in a node's input list
  
      def output(x):
          return x * x
  
      rng = np.random.RandomState([2012, 8, 28])
  
      vx = rng.randn(2)
  
      theano.tests.unittest_tools.verify_grad(output, [vx])
  
imports: from __future__ import absolute_import, print_function, division
  from collections import OrderedDict
  import unittest
  import numpy
  from six.moves import xrange
  import theano
  from theano import gof, change_flags
  from theano.compat import izip
  from theano.tests import unittest_tools
  from theano import gradient
  from theano import config
  from theano.gof.null_type import NullType
  from theano.sandbox.rng_mrg import MRG_RandomStreams
label_desc: Use image node_id 6 for calling the test_grad obj's underlying member method code with example usage: obj.test_grad_duplicate_input() and returns: unknown