public function add_submenu_toggle_attributes( $attributes, $context, $args ) {

    $state_id      = esc_attr( $args['state_id'] );
    $submenu_index = esc_attr( $args['submenu_index'] );
    $classes       = isset( $attributes['class'] ) ? $attributes['class'] : $context;
    $classes       = esc_attr( "{$classes} {$this->script_config['subMenuIconClass']}" );

    $attributes['class']         = $classes;
    $attributes['aria-expanded'] = 'false';
    $attributes['aria-pressed']  = 'false';

    /*
		 * Add the AMP event bindings.
		 * In the 'on' attribute, toggle between the $submenu_index and 0 (not expanded).
		 * There can only be one menu item in each menu depth expanded at a time.
		 * For example, if there are 4 primary menu items, only one of them can have its submenu expanded.
		 */
    $attributes['on']              = "tap:AMP.setState( { {$state_id}: {$state_id} == {$submenu_index} ? {$this->submenu_not_expanded} : {$submenu_index} } )";
    $attributes['[class]']         = "{$state_id} == {$submenu_index} ? '{$classes} activated toggled-on' : '{$classes}'";
    $attributes['[aria-expanded]'] = "{$state_id} == {$submenu_index} ? 'true' : 'false'";
    $attributes['[aria-pressed]']  = $attributes['[aria-expanded]'];

    return $attributes;

  }