def METHOD_NAME(self):
    a = A()
    dict_trait = a.traits()["adict"]
    self.assertEqual(dict_trait.default, {"a": 1, "b": 2})
    # The default property should have returned a copy, so
    # modifying it doesn't change the actual default.
    dict_trait.default.pop("a")
    self.assertEqual(a.adict, {"a": 1, "b": 2})