[Python] File3dmObjectTable.__getitem__() does not accept negative indexing

[StudioWEngineers]

In Python negative indexing is possible, so I would expect this to work:

import rhino3dm

model = rhino3dm.File3dm()

for i in range(2):
    model.Objects.AddPoint(rhino3dm.Point3d(i, 0, 0))
    print(model.Objects[-1].Geometry.Location)

print(model.Objects[-2].Geometry.Location)

However, this does not work because of:

rhino3dm/src/bindings/bnd_extensions.cpp

Line 674 in 2be2968

throw pybind11::index_error();

I would be happy to prepare a PR to make the behaviour of File3dmObjectTable.__getitem__() closer to a Python list, but I am wondering if this would be considered acceptable.

[sbaer]

I don't see any downside to supporting negative indexing