def register(self, change_callback):
        self._change_callbacks.append(change_callback)
skipws will skip whitespaces.
dataset/ETHPy150Open ClusterHQ/flocker/flocker/control/_persistence.py/ConfigurationPersistenceService.register--crossover with--dataset/ETHPy150Open igordejanovic/Arpeggio/tests/unit/test_parser_params.py/test_skipws