static <A> MultiMap<S, A> ciMultiMapFromKeyAndValueField(Collection l, S keyField, S valueField) {
  MultiMap<S, A> mm = ciMultiMap();
  if (l != null) for (O o : l)
    mm.put((S) getOpt(o, keyField), (A) getOpt(o, valueField));
  ret mm;
}