def permanently_delete(self, user):
        """
        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
        """
        url = self._build_url(self.endpoint.deleted(id=user))
        deleted_user = self._delete(url)
        self.cache.delete(deleted_user)
        return deleted_user