code: def save_persistent_attributes(self):
          # type: () -> None
          
          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)
docs: 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