Rhye WordPress Theme: Enable hierarchical categories

<?php

add_filter( 'register_post_type_args', 'custom_cpt_enable_categories_hierarchy', 10, 2 );
function custom_cpt_enable_categories_hierarchy( $args, $post_type ) {

  if ( $post_type === 'arts_portfolio_item' ) {
    $args['hierarchical'] = true;
  }

  return $args;
}

add_filter( 'register_taxonomy_args', 'custom_taxonomy_enable_categories_hierarchy', 10, 3 );
function custom_taxonomy_enable_categories_hierarchy( $args, $taxonomy, $object_type ) {

  if ( $taxonomy === 'arts_portfolio_category' ) {
    $args['hierarchical'] = true;
  }

  return $args;
}