How to use the @material/dialog/foundation.strings function in @material/dialog

mounted() {
    const strings = MDCDialogFoundation.strings;

    const { open, autoStackButtons, escapeKeyAction, scrimClickAction } = this;

    this.buttons_ = [].slice.call(this.$el.querySelectorAll(cssClasses.BUTTON));
    this.defaultButton = this.$el.querySelector(
      `[${strings.BUTTON_DEFAULT_ATTRIBUTE}]`,
    );

    const adapter = {
      addClass: className => this.$set(this.classes, className, true),
      removeClass: className => this.$delete(this.classes, className),
      hasClass: className => this.$el.classList.contains(className),
      addBodyClass: className => document.body.classList.add(className),
      removeBodyClass: className => document.body.classList.remove(className),
      eventTargetMatches: (target, selector) => matches(target, selector),
      trapFocus: initialFocusEl => this.focusTrap && this.focusTrap.activate(),

getInitialFocusEl_() {
      return document.querySelector(
        `[${MDCDialogFoundation.strings.INITIAL_FOCUS_ATTRIBUTE}]`,
      );
    },
    onOpen_(value) {

mounted() {
    const strings = MDCDialogFoundation.strings;

    const { open, autoStackButtons, escapeKeyAction, scrimClickAction } = this;

    this.buttons_ = [].slice.call(this.$el.querySelectorAll(cssClasses.BUTTON));
    this.defaultButton = this.$el.querySelector(
      `.${cssClasses.DEFAULT_BUTTON}`,
    );

    const adapter = {
      addClass: className => this.$set(this.classes, className, true),
      removeClass: className => this.$delete(this.classes, className),
      hasClass: className => this.$el.classList.contains(className),
      addBodyClass: className => document.body.classList.add(className),
      removeBodyClass: className => document.body.classList.remove(className),
      eventTargetMatches: (target, selector) => matches(target, selector),
      trapFocus: () => this.focusTrap && this.focusTrap.activate(),