def test_single_assignment(self):
    varz = self.Varz({'meaning of life': 42})
    with self.assertRaises(MutationError):
        varz.varz = {'fine structure constant': (1 / 137.0)}
def test_single_assignment(self):
    varz = self.Varz({'meaning of life': 42})
    with self.assertRaises(MutationError):
        varz.varz = {'fine structure constant': (1 / 137.0)}