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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def keys(self):
 """Return a list of attribute names for the mapping. :rtype: list """

        return sorted([k for k in dir(self) if
                       k[0:1] != '_' and k != 'keys' and not k.isupper() and
                       not inspect.ismethod(getattr(self, k)) and
                       not (hasattr(self.__class__, k) and
                            isinstance(getattr(self.__class__, k),
                                       property)) and
                       not isinstance(getattr(self, k), property)])