protected function find_and_combine() {

    foreach ( $this->menus_to_combine as $attribute ) {
      $nav_menu = $this->find_nav_ul( $attribute );
      if ( ! $nav_menu ) {
        continue;
      }

      // Clone to avoid removing from current menu.
      $menu_items = $nav_menu->cloneNode( true );

      // Combine the menu items with the main menu.
      // phpcs:disable WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase
      for ( $index = 0; $index < $menu_items->childNodes->length; $index++ ) {
        $menu_item = $menu_items->childNodes->item( $index );

        // Skip if this is not an element node.
        if ( ! ( $menu_item instanceof DOMElement ) ) {
          continue;
        }

        // Set a class attribute to hide when viewport is larger than responsive width.
        $menu_item->setAttribute( 'class', 'genesis-amp-combined ' . $menu_item->getAttribute( 'class' ) );

        $this->main_menu->appendChild( $menu_item );
      }
      // phpcs:enable
    }

  }