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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 persistent_attributes(self):
 # type: () -> Dict[str, object] """Attributes stored at the Persistence level of the skill lifecycle. :return: persistent_attributes retrieved from persistence adapter :rtype: Dict[str, object] :raises: :py:class:`ask_sdk_core.exceptions.AttributesManagerException` if trying to get persistent attributes without persistence adapter """

        if not self._persistence_adapter:
            raise AttributesManagerException(
                "Cannot get PersistentAttributes without Persistence adapter")
        if not self._persistent_attributes_set:
            self._persistence_attributes = (
                self._persistence_adapter.get_attributes(
                    request_envelope=self._request_envelope))
            self._persistent_attributes_set = True
        return self._persistence_attributes