docs: private Result getModelLastUpdateTimes(String modelIDs){
  
          if(currentSessionID == null){
              return ok();
          }
  
          StatsStorage ss = knownSessionIDs.get(currentSessionID);
          if(ss == null){
              log.debug("getModelLastUpdateTimes(): Session ID is unknown: {}", currentSessionID);
              return ok("-1");
          }
  
          String[] split = modelIDs.split(",");
  
          long[] lastUpdateTimes = new long[split.length];
          for( int i=0; i<split.length; i++ ){
              String s = split[i];
              Persistable p = ss.getLatestUpdate(currentSessionID, ARBITER_UI_TYPE_ID, s);
              if(p != null){
                  lastUpdateTimes[i] = p.getTimeStamp();
              }
          }
  
          return ok(Json.toJson(lastUpdateTimes));
      }