def test_truthiness(self):
        """
        Empty flags is false, non-empty flags is true.
        """
        self.assertTrue(self.FXF.WRITE)
        self.assertTrue(self.FXF.WRITE | self.FXF.EXCLUSIVE)
        self.assertFalse(self.FXF.WRITE & self.FXF.EXCLUSIVE)

        Empty flags is false, non-empty flags is true.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_constants.py