def RegionPack(region_id, center=None, verts=None):
    """ This function packs a region_id and the constructor overrides for that Region
        into a tuple. Only center or verts can be overridden currently and only one of
        those per Region. The resulting tuple looks like:
        (region_id, {region_constructor_args}) """
    region_args = {}
    if center != None:
        assert verts is None
        region_args['center'] = center
    if verts != None:
        assert center is None
        region_args['verts'] = verts
    return (region_id, region_args)