String key = stem + ":" + group;
String key = Stem.constructName(stem, group);
  protected Group getGroup(String stem, String group)     throws  Exception  {    String key = stem + ":" + group; // FIXME     if (this.groups.containsKey(key)) {      return (Group) this.groups.get(key);    }    throw new Exception("group not found: " + key);  } // protected Group getGroup(stem, group)