String getStringKey(UsersGroupsPK value) {
   StringBuilder sb = new StringBuilder();
   sb.append(value.getGroupName());
   sb.append(SEPARATOR);
   sb.append(value.getUserId());
   return sb.toString();
 }
 UsersGroupsPK getKey(String value) {
   UsersGroupsPK key;
   String values[] = value.split(SEPARATOR_ESCAPED);
   key = new UsersGroupsPK();
   key.setGroupName(values[0]);
   key.setUserId(Integer.parseInt(values[1]));
   return key;
 }