static Collection<Sym> ai_expandShortenedKeys(Sym sKey) {
  if (!endsWith(sKey, "...")) ret ll(sKey);
  new LinkedHashSet<Sym> set;
  for position to 3:
    for (TripleRef<Symbol> r : unnull(tripleIndex().getTripleRefs(sKey, position)))
      if (r != null) set.add(r!);
  ret set;
}