In Stalker, classes mixed with StatusMixin needs to be created with a suitable StatusList instance.
Because most of the statusable classes are going to be using the same Statuses (ex: WIP, Waiting Review, Completed etc.) over and over again, it is much efficient to create those Statuses only once and use them multiple times by grouping them in StatusLists.
A suitable status list means, the target_entity_type is set to the name of that particular class.