code: protected void throwListUnsupportedActionException() throws CmsRuntimeException {
  
          throw new CmsRuntimeException(
              Messages.get().container(
                  Messages.ERR_LIST_UNSUPPORTED_ACTION_2,
                  getList().getName().key(getLocale()),
                  getParamListAction()));
      }
docs: A convenient method to throw a list unsupported
  action runtime exception.<p>
  
  Should be triggered if your list implementation does not
  support the <code>{@link #getParamListAction()}</code>
  action.<p>
  
  @throws CmsRuntimeException always to signal that this operation is not supported