How to use the @egjs/flicking.DEFAULT_OPTIONS.classPrefix function in @egjs/flicking

public render(h: CreateElement) {
    const classPrefix = this.options.classPrefix || DEFAULT_OPTIONS.classPrefix;
    const viewportData: VNodeData = {
      class: {},
    };
    const cameraData: VNodeData = {
      class: {},
      directives: [{ name: "children-differ", value: this.onUpdate.bind(this) }],
    };
    viewportData.class[`${classPrefix}-viewport`] = true;
    cameraData.class[`${classPrefix}-camera`] = true;

    const panels = this.$_getPanels(h);

    return h(this.tag,
      [h("div", viewportData,
        [h("div", cameraData,
          panels,