def setUp(self):
        """
        Keep track of all boxes received by this test in its capacity as an
        L{IBoxReceiver} implementor.
        """
        self.boxes = []
        self.data = []

        Keep track of all boxes received by this test in its capacity as an
        L{IBoxReceiver} implementor.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_amp.py