How to use the translators.object.ObjectKey function in translators

def __create_dupli_instances(self, obj, scene, settings):
        with DupliListBuilder(obj, scene, settings):
            for dupli in obj.dupli_list:
                # Create translators for dupli instances.
                if dupli.object.type == 'MESH':
                    obj_key = ObjectKey (dupli.object)
                    mesh_key = ObjectKey(dupli.object.data)

                    is_modified = dupli.object.is_modified(scene, 'RENDER')

                    if is_modified == False and mesh_key in self.__datablock_to_translator:
                        logger.debug("Creating instance translator for object %s, master obj: %s", obj_key, mesh_key)

                        master_translator = self.__datablock_to_translator[mesh_key]
                        self.__object_translators.append(InstanceTranslator(dupli.object, master_translator, self.asset_handler))
                        master_translator.add_instance()
                    else:
                        logger.debug("Creating mesh translator for object %s", obj_key)

                        translator = MeshTranslator(dupli.object,
                                                    self.__export_mode,
                                                    self.asset_handler)

def __create_dupli_instances(self, obj, scene, settings):
        with DupliListBuilder(obj, scene, settings):
            for dupli in obj.dupli_list:
                # Create translators for dupli instances.
                if dupli.object.type == 'MESH':
                    obj_key = ObjectKey (dupli.object)
                    mesh_key = ObjectKey(dupli.object.data)

                    is_modified = dupli.object.is_modified(scene, 'RENDER')

                    if is_modified == False and mesh_key in self.__datablock_to_translator:
                        logger.debug("Creating instance translator for object %s, master obj: %s", obj_key, mesh_key)

                        master_translator = self.__datablock_to_translator[mesh_key]
                        self.__object_translators.append(InstanceTranslator(dupli.object, master_translator, self.asset_handler))
                        master_translator.add_instance()
                    else:
                        logger.debug("Creating mesh translator for object %s", obj_key)

                        translator = MeshTranslator(dupli.object,
                                                    self.__export_mode,
                                                    self.asset_handler)

master_translator = self.__datablock_to_translator[mesh_key]
                        self.__object_translators.append(InstanceTranslator(dupli.object, master_translator, self.asset_handler))
                        master_translator.add_instance()
                    else:
                        logger.debug("Creating mesh translator for object %s", obj_key)

                        translator = MeshTranslator(dupli.object,
                                                    self.__export_mode,
                                                    self.asset_handler)

                        self.__object_translators.append(translator)

                        for slot in dupli.object.material_slots:
                            mat = slot.material
                            mat_key = ObjectKey(mat)

                            if mat_key not in self.__material_translators:
                                logger.debug("Creating material translator for material %s", mat_key)
                                mat_translator = MaterialTranslator(mat, self.asset_handler)
                                self.__material_translators[mat_key] = mat_translator
                                mat_translator.create_entities(scene)

                        if not is_modified:
                            logger.debug("Saving translator for object %s in instance map", obj_key)
                            self.__datablock_to_translator[mesh_key] = translator
                else:
                    logger.debug("Skipping unsupported dupli source object of type %s", dupli.object.type)

            # Create dupli instances entities.
            for translator in self.__object_translators:
                translator.create_entities(scene)