The __slots__ documentation in the datamodel needs improvement.

For example:

> When inheriting from a class without __slots__, the __dict__ attribute of that class will always be accessible, so a __slots__ definition in the subclass is meaningless.

The __slots__ definition for such a subclass is not meaningless: other slots declared will still be used, and the __dict__ will not be instantiated unless it is looked for (although this may be an implementation detail).

> The action of a __slots__ declaration is limited to the class where it is defined. As a result, subclasses will have a __dict__ unless they also define __slots__ (which must only contain names of any additional slots).

That's not quite right either. The action of a __slots__ declaration is not entirely limited to the class where it is defined. They can have implications for multiple inheritance, and child classes will have access to those slots.

I have some changes I'd like to make to the entire section on __slots__, and I'll be providing a pull request soon.