def METHOD_NAME(self):
    a = A()
    set1 = copy.deepcopy(a.aset)
    self.assertIsNone(set1.object())
    set1.add(10)
    self.assertEqual(len(a.events), 0)
    a.aset.add(20)
    self.assertEqual(len(a.events), 1)
    set2 = copy.deepcopy(set1)
    set2.add(30)
    self.assertIsNone(set2.object())
    set3 = a.aset.copy()
    self.assertIs(type(set3), set)
    # Should not raise an AttributeError:
    set3.remove(20)