wp-includes/class-wp-duotone.php:616Get the ID of the duotone filter.
$slugstringstring private static function get_filter_id( $slug ) { return "wp-duotone-$slug"; }Introduced in 6.3.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-duotone.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.