The Fiona 7 release_collector makes it possible to specify custom release patterns for CMS objects. So, for example, if releasing a page should cause some other page to be released as well (e.g. one that isn't referenced), then this functionality can be used to achieve the desired behavior.
The release_collector accepts anything responding to the call method and expects one parameter: obj_id. Thus, it is possible to use a lambda, like so: