I'm -1 on making ANY guarantees about which methods underlie others -- that would constitute new and everlasting guarantees about how mappings are implemented.  Subclasses should explicity override/extend the methods withed changed behavior.  If that proves non-trivial, then it is likely there should be a has-a relationship instead of an is-a relationship.  Also, it is likely that the subclass will have Liskov substitutability violations.  Either way, there is probably a design flaw.