> True ... unless someone had defined a subclass of DimCoord.

Of course.

Why not call ```DimCoord.__new__()``` directly rather than the method from its superclass? That should allow for future customisation of ```DimCoord.__new__()``` as well as ```super(DimCoord, cls).__new__()``` (I'm assuming ```DimCoord.__new__()``` will call ```super(DimCoord, cls).__new__()```).