def METHOD_NAME(self):
    import operator
    sd = SortedAndFixedKeysDict({'a':1, 'b':[3]})
    self.assertEqual(sd['a'],1)
    self.assertEqual(sd['b'],[3])
    self.assertRaises(AttributeError,operator.setitem,*(sd,'a',2))
    sd = SortedAndFixedKeysDict([('a',1), ('b',2),('a',3)])
    self.assertEqual(['a','b'], [x for x in iter(sd)])