This is exploring a pattern for a stateful class.  An alternative idea
would be to actually dispatch on a "state" object every time (making
the dispatching a real multiple dispatching, I guess).

This is conceptually:
* When a given method is called dispatch once to find the implementation.
* After this, on any method/property use, forward to the implementation.
  (This includes the initial method call itself.)

The once dipatching is a normal dispatching function, just a different
decorator because the default is to do nothing (and not to call the
function).