Class AttributeWithUnique

source code

Container which also takes care about recomputing unique values

XXX may be we could better link original attribute to additional attribute which actually stores the values (and do reverse there as well).

Pros:

• don't need to mess with getattr since it would become just another attribute

Cons:

• might be worse design in terms of comprehension
• take care about _set, since we shouldn't allow change it externally

For now lets do it within a single class and tune up getattr