def METHOD_NAME(self):
    # baseline behavior for a defaultdict
    _dd = defaultdict(list)
    _dd["a"]
    self.assertEqual(_dd, {"a": []})
    # behavior after defaultdict is set as attribute
    dd = defaultdict(list)
    self.obj.db.test = dd
    self.obj.db.test["a"]
    self.assertEqual(self.obj.db.test, {"a": []})
    self.obj.db.test["a"].append(1)
    self.assertEqual(self.obj.db.test, {"a": [1]})
    self.obj.db.test["a"].append(2)
    self.assertEqual(self.obj.db.test, {"a": [1, 2]})
    self.obj.db.test["a"].append(3)
    self.assertEqual(self.obj.db.test, {"a": [1, 2, 3]})
    self.obj.db.test |= {"b": [5, 6]}
    self.assertEqual(self.obj.db.test, {"a": [1, 2, 3], "b": [5, 6]})