There are a few APIs on Skeleton that return lists of raw pointers to internal Skeleton data (BodyNodes and Joints) to Python. These APIs need to have the List object itself get garbage collected when Python is no longer using it, but _not_ the individual contents of the List, because that is still in use by C++. Unfortunately, Pybind11 does not yet have support for doing this, so we've disabled the APIs for now. Instead, you can use things like `[skel.getBodyNode(i) for i in range(skel.getNumBodyNodes())]`