code: def test_single_var(self):
      # Test `is_same_graph` with some trivial graphs (one Variable).
  
      x, y, z = tensor.vectors("x", "y", "z")
      self.check(
          [
              (x, x, (({}, True),)),
              (
                  x,
                  y,
                  (
                      ({}, False),
                      ({y: x}, True),
                  ),
              ),
              (x, tensor.neg(x), (({}, False),)),
              (x, tensor.neg(y), (({}, False),)),
          ]
      )
  
imports: from __future__ import absolute_import, print_function, division
  from itertools import count
  import pickle
  import unittest
  from nose.plugins.skip import SkipTest
  import numpy
  from theano import sparse, shared, tensor
  from theano.gof.graph import Apply, as_string, clone, general_toposort, inputs, io_toposort, is_same_graph, Variable
  from theano.gof.op import Op
  from theano.gof.type import Type
label_desc: Use image node_id 2 for calling the TestIsSameGraph obj's underlying member method code with example usage: obj.test_single_var() without return types