get_css_custom_property_name example

    private static function get_css_var( $slug ) {
        $name = self::get_css_custom_property_name( $slug );
        return "var($name)";
    }

    /** * Get the URL for a duotone filter. * * Example output: * url(#wp-duotone-blue-orange) * * @internal * * @since 6.3.0 * * @param string $filter_id The ID of the filter. * @return string The URL for the duotone filter. */