def serialize(self, obj):
        """Serialize an object for sending to the front-end."""
        if hasattr(obj, '_jsid'):
            return {'immutable': False, 'value': obj._jsid}
        else:
            obj_json = {'immutable': True}
            try:
                json.dumps(obj)
                obj_json['value'] = obj
            except:
                pass
            if callable(obj):
                guid = str(uuid.uuid4())
                callback_registry[guid] = obj
                obj_json['callback'] = guid
            return obj_json
Serialize an object for sending to the front-end.