code: def testImmutableCppDescriptor(self):
      message_descriptor = unittest_pb2.TestAllTypes.DESCRIPTOR
      with self.assertRaises(AttributeError):
          message_descriptor.fields_by_name = None
      with self.assertRaises(TypeError):
          message_descriptor.fields_by_name["Another"] = None
      with self.assertRaises(TypeError):
          message_descriptor.fields.append(None)
  
imports: import sys
  from google.protobuf import unittest_custom_options_pb2
  from google.protobuf import unittest_import_pb2
  from google.protobuf import unittest_pb2
  from google.protobuf import descriptor_pb2
  from google.protobuf.internal import api_implementation
  from google.protobuf.internal import test_util
  from google.protobuf import descriptor
  from google.protobuf import descriptor_pool
  from google.protobuf import symbol_database
  from google.protobuf import text_format
label_desc: Use image node_id 15 for calling the DescriptorTest obj's underlying member method code with example usage: obj.testImmutableCppDescriptor() without return types