How to get return binding Attribute for Azure FunctionApp binding

I have function:

[FunctionName("test-function")]
        [return: ServiceBus("topic-name", Connection = "connection-string")]
        public static Task<Message> TestFunction([TimerTrigger("%TimerSchedule%")]TimerInfo timer, ILogger log)
        {
            return Task.FromResult(new Message());
        }

How can I get ServiceBus attribute through reflecion as it is not part of methods CustomAttributes collection?