STL connectivity
 

I'm trying to find a way to check if two stl's are coincident (python preferred).
Let's say I have to parts, a cube with a central cutout in the shape of a triangular pyramid, and a triangular pyramid that fits into that cutout.
The correct parts should fit, but an incorrect part (say if you put a cube into the cutout) should be flagged.

So far I have found no ways of doing this.

Thanks for suggestions.