Find Families w/ Imported DWG geometry

We are trying to clean up our family library. At the moment, we have placed all of our families in one Revit file where we can rename, inspect and clean up the families we want to keep.

We have some very old families that are essentially just a shell for an imported 3D DWG file. Is there a way that Dynamo can detect which placed families contain imported geometry? It would be nice to get rid of all of these (or at least call them out) in one swoop.

Thanks,

Aaron