code: public void prepareParameters(Map<String, Object> extra) {
          if (paramConfig == null) return;
          for (ParamConfig param : paramConfig)
          {
              param.prepareParameter(extra);
          }
      }
docs: Prepares the parameters for the report. This populates the Combo and ManyCombo box options if there is a groovy
  or report backing the data.
  @param extra Extra options from the middleware, this is passed down to the report or groovy execution.