MasterPress 1.3.1 is a compatibility release for PHP 8 and WordPress 5.7. It still remains backwards compatible with older PHP versions.
WOOF_Taxonomy :: find_or_create( String $slug )
Retrieves a term object in this taxonomy by first trying to find a term with the specified $slug, or creating a new term with the specified slug if not found.
This method could be very useful in some kind of import process, where you might want to create or update terms from another data source (such as a JSON API) without needing to worry about checking for existence first (see example).