def tearDown(self):
        if hasattr(self.page, '_messageDeliverer'):
            self.page._messageDeliverer.close()
Registry.clear: removes all keys.
dataset/ETHPy150Open twisted/nevow/nevow/test/test_athena.py/LivePageTests.tearDown--crossover with--dataset/ETHPy150Open xtrementl/focus/tests/unit/test_registry.py/TestRegistry.test__clear