WordPress: Exclude posts if they are only tagged in a single category (Plugin)

gistfile1.php

<?php

/*
Plugin Name: Exclude Posts if in Single Category
Description: Exclude posts if they are only tagged in a single category, as defined by the category number. This will show posts in the loop if they are tagged in more than one category.
Version: 1.0
Author: Zac Vineyard
Author URI: http://www.zacvineyard.com
*/

function exclude_category($query)
{
    
    $categories = get_categories(array('exclude' => '46'));

    if (!is_admin())
    {
        $query->set('cat', '-46');
        $cat_ids = array();
        foreach ($categories as $category) {
            $cat_ids[] = $category->term_id;
        }
        $include = implode(",", (array) $cat_ids);
        $query->set('cat', $include);
    }
    return $query;
}

add_filter('pre_get_posts', 'exclude_category');

?>