> class A(HasTraits):
> a = This
> cTrait = A.class_traits()['a']
> I can find out "This" easily from cTrait:
> cTrait.handler.__class__ == This
> How do I find out that the self_class is A, starting with just cTrait?
That information is not actually stored in the trait itself.
This.validate() gets passed the both `self` and the value being
assigned, and the validation happens dynamically.