Unregister custom post type from Wordpress

Question

I'm trying to remove a custom post type that was set via a different theme in Wordpress, now all of those posts are assigned to a post_type of portfolio. After a lot of searching, I found the code below, however it doesn't seem to work. I tried adding it both to the new theme and the old themes functions.php.

I want to remove the post_type and have the posts categorized and displayed as a normal post. I think what I'm doing is correct, but can't seem to get it to work - I've posted both the code for the custom post type and the code to unregister the posts assigned to it.

Code to uregister post type

if ( ! function_exists( 'unregister_post_type' ) ) :
function unregister_post_type() {
global $wp_post_types;
if ( isset( $wp_post_types[ 'portfolio' ] ) ) {
    unset( $wp_post_types[ 'portfolio' ] );
    return true;
}
return false;
}
endif;

add_action('init', 'unregister_post_type');

Code that registered the post type

register_post_type( 'portfolio',
    array(
        'labels' => array(
             'name' => __('Portfolio Items'),
             'singular_name' => __('Portfolio Item'),
             'add_new_item' => __('Add New Portfolio Item'),
             'edit_item' => __('Edit Portfolio Item'),
             'new_item' => __('New Portfolio Item'),
             'view_item' => __('View Portfolio Item'),
             'search_items' => __('Search Portfolio Items'),
             'not_found' => __('No portfolio items found'),
             'not_found_in_trash' => __('No portfolio items found in Trash')
        ),
        'public' => true,
        'show_ui' => true,
        'hierarchical' => false,
        'menu_position' => 7,
        //'rewrite' => array('slug' => 'portfolio'),
        'rewrite' => true,
        '_built_in' => false,
        'taxonomies' => array( 'post_tag','category','portfolio_tag', 'portfolio_category', 'client'),
        'supports' => array( 'title','editor','author','thumbnail','excerpt','trackbacks','custom-fields','comments','revisions')
    )
);

Answer 1

I was able to remove it in WordPress 4.6.1 using this code:

function delete_post_type(){
  unregister_post_type( 'portfolio' );
}
add_action('init','delete_post_type', 100);