Child_of Taxonomy

I can see that if we edit the “mctagmap_functions.php” and add parent=ID I can achieve it. But what must we edit in that file to make it possible to insert it via shortcode and choose the desired tag_ID to be possible to make several different Indexes?

if($taxonomy){
		$tags = get_terms($taxonomy, 'order=ASC&<strong>parent=ID</strong>&hide_empty='.$show_empty.'');