code: def test_eval(self):
      self.assertEqual(self.w.eval({self.x: 1.0, self.y: 2.0}), 6.0)
      self.assertEqual(self.w.eval({self.z: 3}), 6.0)
      self.assertTrue(
          hasattr(self.w, "_fn_cache"),
          "variable must have cache after eval",
      )
      self.assertFalse(
          hasattr(pickle.loads(pickle.dumps(self.w)), "_fn_cache"),
          "temporary functions must not be serialized",
      )
  
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 TestEval obj's underlying member method code with example usage: obj.test_eval() without return types