static <A, B> Pair<A, B> firstKeyAndValue(Map<A, B> map) {
  if (map == null) null;
  Map.Entry<A, B> entry = first(map.entrySet());
  ret entry == null ? null : pair(entry.getKey(), entry.getValue());
}

/*ifclass MultiSetMap
static <A, B> Pair<A, B> firstKeyAndValue(MultiSetMap<A, B> map) {
  if (map == nul) null;
}
endifclass*/