Highlight custom post type parent as active item in Wordpress Navigation

index.php

function remove_parent($var)
{
if ($var == 'current_page_parent' || $var == 'current-menu-item' || $var == 'current-page-ancestor') { return false; }
return true;
}

function tg_add_class_to_menu($classes)
{
if (is_singular('projects'))
{
  $classes = array_filter($classes, "remove_parent");

  if (in_array('menu-item-194', $classes)) $classes[] = 'current-page-ancestor';
}
elseif (is_singular('blog'))
{
  $classes = array_filter($classes, "remove_parent");

  if (in_array('menu-item-196', $classes)) $classes[] = 'current-page-ancestor';
}
elseif (is_singular('library'))
{
  $classes = array_filter($classes, "remove_parent");

  if (in_array('menu-item-195', $classes)) $classes[] = 'current-page-ancestor';
}
elseif (is_singular('travel'))
{
  $classes = array_filter($classes, "remove_parent");

  if (in_array('menu-item-192', $classes)) $classes[] = 'current-page-ancestor';
}

return $classes;
}

if (!is_admin()) { add_filter('nav_menu_css_class', 'tg_add_class_to_menu'); }