code: def permanently_delete(self, user):
          
          url = self._build_url(self.endpoint.deleted(id=user))
          deleted_user = self._delete(url)
          self.cache.delete(deleted_user)
          return deleted_user
docs: Permanently delete user. User should be softly deleted first.
          Zendesk API `Reference <https://developer.zendesk.com/rest_api/docs/core/users#permanently-delete-user>`__.
  
          Note: This endpoint does not support multiple ids or list of `User` objects.
  
          :param user: User object or id.
          :return: User object with `permanently_deleted` status