Unset product post type from categories

gistfile1.phtml

    function unset_preorder_terms( $product ) {
        if ( is_object( $product ) )
            $product = $product->id;

        $terms = wp_get_post_terms($product, 'product_cat');
        $term_ids = array();
        foreach ( $terms as $term ){
            if ( strpos($term->slug, 'pre-order') === false ){
                $term_ids[] = $term->term_id;
            }
        }

        wp_set_post_terms( $product, $term_ids, 'product_cat');
    }