setDisplay(display) {
    if ((this.display === display) && this.instance) {
      return Promise.resolve(this.instance);
    }

    this.form.display = display;
    this.instance.destroy();
    this.instance = this.create(display);
    return this.setForm(this.form).then(() => {
      this.instance.emit('setDisplay', this.form.display)
    });
  }
Changes the display of the form.
@param {string} display - The display to set this form. Either "wizard", "form", or "pdf"
@returns {Promise<Webform|Wizard|PDF>} - The form instance that was created after changing the display.