code: public static Frame getFromDKV(String param_name, Key key) {
      if (null == key)
        throw new H2OIllegalArgumentException(param_name, "Frames.getFromDKV()", null);
  
      Value v = DKV.get(key);
      if (null == v)
        throw new H2OKeyNotFoundArgumentException(param_name, key.toString());
  
      Iced ice = v.get();
      if( ice instanceof Vec )
        return new Frame((Vec)ice);
  
      if (! (ice instanceof Frame))
        throw new H2OKeyWrongTypeArgumentException(param_name, key.toString(), Frame.class, ice.getClass());
  
      return (Frame)ice;
    }
docs: TODO: almost identical to ModelsHandler; refactor