Add class to the link before a sub-menu, not the list item before it

I am looking to do almost exactly what this function does in WordPress:

`add_filter(‘wp_nav_menu_objects’, function ($items) {
$hasSub = function ($menu_item_id, &$items) {
foreach ($items as $item) {
if ($item->menu_item_parent && $item->menu_item_parent==$menu_item_id) {
return true;
}
}
return false;
};

foreach ($items as &$item) {
if ($hasSub($item->ID, &$items)) {
$item->classes[] = ‘menu-parent-item’; // all elements of field “classes” of a menu item get join together and render to class attribute of <li> element in HTML
}
}
return $items;
});`

This handy function attaches a class “menu-parent-item” to the li that contains a sub-menu. What I would like to do is add that same class (or any other usable class of course) to the link beforehand instead. In other words I would end up with this:

`<li>
<a href=”index.php” class=”menu-parent-item”>
<ul class=”sub-menu”>
<li>`

And so forth. Any ideas?