def test_SON(self):

        simple_son = SON([])
        complex_son = SON([('son', simple_son), ('list', [simple_son, simple_son])])

        def test_pickling(p):
            pickled = pickle.loads(pickle.dumps(complex_son, protocol=p))
            self.assertEquals(pickled['son'], pickled['list'][0])
            self.assertEquals(pickled['son'], pickled['list'][1])


        for protocol in [0, 1, 2, -1]:
            test_pickling(protocol)