static S multiSetToLines(MultiSet ms) {
  new L<S> l;
  if (ms != null) for (O o : ms.highestFirst())
    l.add(ms.get(o) + ": " + str(o));
  ret lines(l);
}

static S multiSetToLines(Iterable l) {
  ret multiSetToLines(toMultiSet(l));
}