the subclass will have a __dict__ available too.
Notes on using *__slots__*
+* 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.
+
* Without a *__dict__* variable, instances cannot be assigned new variables not
listed in the *__slots__* definition. Attempts to assign to an unlisted
variable name raises :exc:`AttributeError`. If dynamic assignment of new