> R. David Murray added the comment:
> 
> You are conceptualizing this very differently.  In our view, this
> data structure is for cases where the original key is the most
> important piece of information (about the keys).  The transformation
> in the lookup process is entirely in the service of looking up the
> value paired with that original key when there is more than one
> possible representation of that key.  It is the original key that is
> critical when re-serializing the data or otherwise making use of the
> keys for anything other than lookup.  So this is about making the
> data structure succinctly model the problem domain, which is what OO
> is supposed to be good at :)

Thanks for putting it much more convincingly than my python-dev
response :-)