docs: @Override public float[] scoreKey( Object modelKey, String [] colNames, String domains[][], double[] row ) {
      Key key = (Key)modelKey;
      String sk = key.toString();
      Value v = DKV.get(key);
      if (v == null)
        throw new IllegalArgumentException("Key "+sk+" not found!");
      try {
        return scoreModel(v.get(),colNames,domains,row);
      } catch(Throwable t) {
        Log.err(t);
        throw new IllegalArgumentException("Key "+sk+" is not a Model key");
      }
    }