def setUp(self):
        """
        Create a trigger, an argument, and an event to be used by tests.
        """
        self.trigger = lambda x: None
        self.arg = object()
        self.event = base._ThreePhaseEvent()

        Create a trigger, an argument, and an event to be used by tests.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_internet.py