How to Display Custom Taxonomies on WordPress Tag Cloud Widget

 <?php 
 
 // Parameters accepted by tag cloud widget
 // @url http://codex.wordpress.org/Function_Reference/wp_tag_cloud
 
 $args = array(
    'smallest'                  => 8, 
    'largest'                   => 22,
    'unit'                      => 'pt', 
    'number'                    => 45,  
    'format'                    => 'flat',
    'separator'                 => \"\n\",
    'orderby'                   => 'name', 
    'order'                     => 'ASC',
    'exclude'                   => null, 
    'include'                   => null, 
    'topic_count_text_callback' => default_topic_count_text,
    'link'                      => 'view', 
    'taxonomy'                  => 'post_tag', 
    'echo'                      => true,
    'child_of'                  => null
); ?>

<?php
 
//* Display custom taxonomies on WordPress tag cloud widget
 
add_filter('widget_tag_cloud_args','afn_display_custom_tax');
    function afn_display_custom_tax($args) {
    $args = array(
        'taxonomy'  => 'mycustom_tax', 
return $args;
}