21783b57_ython_in_Action__Magic_Methods__Method
[Description] If this is defined as a class attribute, then the callable assigned will be called to create the class instead of type. It can also be used as a module-level attribute, and all old-style classes (without an explicit alternative metaclass or inheriting from a class with a metaclass) will use the callable assigned as their metaclass. A quick way to convert all old-style classes in a module into new-style classes is to add __metaclass__ = type at the start of the module. (It doesn't affect new-style classes, as they inherit type as a metaclass from object.) [Method] 
__metaclass__
IronPython in Action: Magic Methods
Method