def check_underlying_dict(self, d, expected):
        self.assertEqual(d._data, expected)
        self.assertEqual(set(d._original), set(expected))
        self.assertEqual([d._transform(v) for v in d._original.values()],
                         list(d._original.keys()))
Check for implementation details.
dataset/ETHPy150Open fluentpython/example-code/attic/dicts/test_transformdict.py/TransformDictTestBase.check_underlying_dict