Masterpress 1.3.6 is a compatibility release. It resolves an edge case with shared fieldsets not working for MySQL 8 when the fieldset is limited to more than 1 post type or taxonomy or excluding any post types or taxonomies.
WOOF_Site :: network_id()
Retrieves the ID of the network that this site is contained in. Note that WordPress doesn’t have a UI to manage multiple networks of multiple sites out of the box, but there are plug-ins to do this.