sclass HasKeyMap<A, B extends HasKey<A>> /*extends AbstractMap<A, B>*/ implements Iterable<B> {
  new Map<A, B> map;
  
  *() {}
  //*(Map<A, B> map) { putAll(this.map, map); }
  *(Iterable<B> l) { addAll(l); }
  
  void addAll(Iterable<B> l) {
    fOr (b : l) if (b != null) map.put(b.key(), b);
  }
  
  public Iterator<B> iterator() { ret valueIterator(map); }
  
  A firstKey() { ret main firstKey(map); }
  
  public int size() { ret map.size(); }
  
  Set<A> keys aka keySet() { ret map.keySet(); }
}