docs: @Override
    public final void process(final Map<String, Object> pAddParam,
      final IRequestData pRequestData) throws Exception {
      String retrieverName = pRequestData.getParameter("nmRet");
      ICsvDataRetriever ret = this.retrievers.get(retrieverName);
      if (ret == null) {
        throw new ExceptionWithCode(ExceptionWithCode.WRONG_PARAMETER,
          "Can't find retriever " + retrieverName);
      }
      pRequestData.setAttribute("dataTree", ret.getSampleDataRow(pAddParam));
    }