Rate limiting of showFriendship(source, target)


Twitter twitter;
Relationship rls = twitter.showFriendship(source, target);

Is it true that the aforementioned code block is not rate limited? And if yes, could you please explain me why?
I am a new programmer with REST API, with limited experience, and I called the block above a magnitude more times than 180 (the supposed rate limit) without any problem. But I would like to be sure that what I am doing is right and stable.

Thank you.