How to use the itkwidgets.trait_types.PointSetList function in itkwidgets

_scale_factors = NDArray(dtype=np.uint8, default_value=np.array([1, 1, 1], dtype=np.uint8),
                             help="Image downscaling factors.").tag(sync=True, **array_serialization)
    _downsampling = CBool(default_value=False,
                          help="We are downsampling the image to meet the size limits.").tag(sync=True)
    _reset_crop_requested = CBool(default_value=False,
                                  help="The user requested a reset of the roi.").tag(sync=True)
    units = Unicode(
        '',
        help="Units to display in the scale bar.").tag(
        sync=True)
    point_set_representations = List(
        trait=Unicode(),
        default_value=[],
        help="Point set representation").tag(
        sync=True)
    point_sets = PointSetList(
        default_value=None,
        allow_none=True,
        help="Point sets to visualize").tag(
        sync=True,
        **polydata_list_serialization)
    point_set_colors = NDArray(dtype=np.float32, default_value=np.zeros((0, 3), dtype=np.float32),
                               help="RGB colors for the points sets")\
        .tag(sync=True, **array_serialization)\
        .valid(shape_constraints(None, 3))
    point_set_opacities = NDArray(dtype=np.float32, default_value=np.zeros((0,), dtype=np.float32),
                                  help="Opacities for the points sets")\
        .tag(sync=True, **array_serialization)\
        .valid(shape_constraints(None,))
    point_set_representations = List(
        trait=Unicode(),
        default_value=[],