def __setattr__(self, key, obj):
        if key is self.__class__.__dict__: # property access
            object.__setattr__(self, key, obj)
        else:
            return self.__dict__["_mapping"].__setitem__(key, obj)
dataset/ETHPy150Open kdart/pycopia/aid/pycopia/dictlib.py/AttrDictWrapper.__setattr__/operator `in` -> `is`