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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 save_persistent_attributes(self):
 # type: () -> None """Save persistent attributes to the persistence layer if a persistence adapter is provided. :rtype: None :raises: :py:class:`ask_sdk_core.exceptions.AttributesManagerException` if trying to save persistence attributes without persistence adapter """

        if not self._persistence_adapter:
            raise AttributesManagerException(
                "Cannot save PersistentAttributes without "
                "persistence adapter!")
        if self._persistent_attributes_set:
            self._persistence_adapter.save_attributes(
                request_envelope=self._request_envelope,
                attributes=self._persistence_attributes)