Steam API - Get base game feature

Hi, I'm working on a site based on the steam API but I can't figure out how to know when a game needs another game to be playable. I know I can get this with the DLC's but there are some games that are expansions and need another game to play it, but they aren't tagged as "DLCs". i.e Overlord Raising Hell.

So in that case how do I get that information from the steam api? I've searched in many other sites but I can't find what I need, and since this site has de feature of showing when a base game is missed in my account, I wanna know if you guys can help me with that. Thanks :D