code: def testProtoConversion(self):
      # to_proto and from_proto are not supported.
      v = self.create_variable([1, 2])
      with self.assertRaises(TypeError):
          v.to_proto()
      with self.assertRaises(TypeError):
          v.from_proto(variable_def=None)
  
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 25 for calling the _VariableInterfaceTestBase obj's underlying member method code with example usage: obj.testProtoConversion() without return types