text: /**
   * `NotifyingElementMixin`: mixin which fires Polymer-style notification events.
   *
   * @polymer
   * @mixinFunction
   *
   * @param {Class}    superclass
   * @return {Class}
   */
  export const NotifyingElementMixin = superclass => class extends superclass {
    /**
     * Fires a `*-changed` event.
     * @param  {String}     propName Name of the property.
     * @param  {any} value  property value
     */
    notify(propName, value) {
      this.dispatchEvent(
        new CustomEvent(`${propName}-changed`, {
          bubbles: true,
          composed: true,
          detail: { value },
        })
      );
    }
  };
  