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add_filter('nav_menu_css_class', 'unfia_mega_menu_classes', 10, 3);
function unfia_mega_menu_classes($classes, $item, $args) {
    if ($args->theme_location === 'primary') {
        if (in_array('menu-item-has-children', $item->classes)) {
            $classes[] = 'nav-item dropdown';
        } else {
            $classes[] = 'nav-item';
        }
    }
    return $classes;
}

add_filter('nav_menu_link_attributes', 'unfia_mega_menu_link_atts', 10, 3);
function unfia_mega_menu_link_atts($atts, $item, $args) {
    if ($args->theme_location === 'primary') {
        if (in_array('menu-item-has-children', $item->classes)) {
            $atts['class'] = 'nav-link dropdown-toggle';
            $atts['role'] = 'button';
            $atts['data-bs-toggle'] = 'dropdown';
            $atts['aria-expanded'] = 'false';
        } else {
            $atts['class'] = 'nav-link';
        }
    }
    return $atts;
}

add_filter('nav_menu_submenu_css_class', 'unfia_mega_menu_submenu_classes', 10, 3);
function unfia_mega_menu_submenu_classes($classes, $args, $depth) {
    $classes[] = 'dropdown-menu';
    return $classes;
}