Add an entity to the ACL.

        :type entity: :class:`_ACLEntity`
        :param entity: The entity to add to this ACL.

def add_entity(self, entity):
        """Add an entity to the ACL.

        :type entity: :class:`_ACLEntity`
        :param entity: The entity to add to this ACL.
        """
        self._ensure_loaded()
        self.entities[str(entity)] = entity