def get_all_lightfilters(scene):
    """Return a list of all lightfilters in the scene

    Args:
    scene (byp.types.Scene) - scene file to look for lights
    
    Returns:
    (list) - list of all lightfilters
    """

    lightfilters = list()
    for ob in scene.objects:
        if ob.type == 'LIGHT':
            if hasattr(ob.data, 'renderman'):
                if ob.data.renderman.renderman_light_role == 'RMAN_LIGHTFILTER':            
                    lightfilters.append(ob)

    return lightfilters