Returns the codebase for the provided object reference.
A codebase is a location information (for instance, URL), specifying,
where the missing parts of the object code can be downloaded. This
is important for the value type objects that handle they method calls
locally and hence must have the local copy of the implementing code.
This implementation expects that the object delegate is set and is
an instance of the org.omg.CORBA_2_3.portable.Delegate. If casts
the set delegate to the given type and invokes
Delegate.get_codebase(org.omg.CORBA.Object)
.