How can I extend this function to check if the current custom post type is in descendent category

I use the following function to check whether the viewed post is in a descendant category of the given ID.

How can i extend the function to also check if the current viewed "custom post type" is in a descendant category of the given ID?

I use this function to set a menu item to "active".

The function is:

/**
  * Tests if any of a post's assigned categories are descendants of target categories
  *
  * @param int|array $cats The target categories. Integer ID or array of integer IDs
  * @param int|object $_post The post. Omit to test the current post in the Loop or main quer开发者_StackOverflowy
  * @return bool True if at least 1 of the post's categories is a descendant of any of the target categories
  * @see get_term_by() You can get a category by name or slug, then pass ID to this function
  * @uses get_term_children() Passes $cats
  * @uses in_category() Passes $_post (can be empty)
  * @version 2.7
  * @link http://codex.wordpress.org/Function_Reference/in_category#Testing_if_a_post_is_in_a_descendant_category
  */
function post_is_in_descendant_category( $cats, $_post = null )
{
 foreach ( (array) $cats as $cat ) {
  // get_term_children() accepts integer ID only
  $descendants = get_term_children( (int) $cat, 'category');
  if ( $descendants && in_category( $descendants, $_post ) )
   return true;
 }
 return false;
}

Thanks in advance!

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Doesn't this work with Custom Post Types? Have you tried?