code: def testHash(self):
      v = self.create_variable()
      w = self.create_variable()
      d = {}
      with self.assertRaises(TypeError):
          d[v] = 1
      d[v.ref()] = 1
      self.assertEqual(d[v.ref()], 1)
      self.assertNotIn(w.ref(), d)
  
imports: from absl.testing import parameterized
  from tensorflow.python.distribute import combinations
  from tensorflow.python.distribute import strategy_combinations
  from tensorflow.python.distribute import test_util
  from tensorflow.python.distribute import values_v2
  from tensorflow.python.eager import def_function
  from tensorflow.python.eager import test
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import indexed_slices
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import resource_variable_ops
  from tensorflow.python.ops import variables
label_desc: Use image node_id 18 for calling the _VariableInterfaceTestBase obj's underlying member method code with example usage: obj.testHash() without return types