def get_light_group(light_ob, scene):
    """Return the name of the lightGroup for this
    light, if any

    Args:
    light_ob (bpy.types.Object) - object we are interested in
    scene (byp.types.Scene) - scene file to look for lights

    Returns:
    (str) - light group name
    """

    scene_rm = scene.renderman
    for lg in scene_rm.light_groups:
        for member in lg.members:
            if light_ob == member.light_ob:
                return lg.name
    return ''