Getting a boundingBox as an input in a node



I need to get a polygonal mesh and its bounding box as my input in a node. I’ve managed to plug-in a mesh but I can’t get to its bounding box. I could set the bounding box as one of my input attributes instead (maybe I even should do this - I’m not sure, I’m still getting used to maya api) but I don’t know how to do that either.
I would appreciate it, if you could give me a hint here. Or point me to the right spot in the documentation.