static Set keys(Map map) { ret map == null ? new HashSet : map.keySet(); } // convenience shortcut for keys_gen static Set keys(O map) { ret keys((Map) map); } ifclass MultiSet static Set keys(MultiSet ms) { ret ms == null ?: ms.keySet(); } endif ifclass IMultiMap static Set keys(IMultiMap mm) { ret mm == null ?: mm.keySet(); } endif ifclass SmallestListMultiMap static Set keys(SmallestListMultiMap mm) { ret mm == null ?: mm.keySet(); } endif