We should keep the BaseOperationsLayer at the front of the bases declaration.

Per python's new-style class MRO, the left-most and lowest occurring class in a hierarchy will have its method selected first at resolution time. So, to ensure that the BaseOperationsLayer.__init__ is always called first, we should keep it as the first item in this bases declaration. Under certain circumstances, the __init__ could be completely skipped — say, if someone decided to add an __init__ to the Extensible mixin, or added a new base to this class at the front of the bases declaration.

Excellent point. Updates made @thedodd . Will merge once checks complete.