code: def listDataTypes(self, datatype="", dataset=""):
          
          try:
              return  self.dbsDataType.listDataType(dataType=datatype, dataset=dataset)
          except dbsException as de:
              dbsExceptionHandler(de.eCode, de.message, self.logger.exception, de.serverError)
          except Exception as ex:
              sError = "DBSReaderModel/listDataTypes. %s\n. Exception trace: \n %s" \
                      % (ex, traceback.format_exc())
              dbsExceptionHandler('dbsException-server-error', dbsExceptionCode['dbsException-server-error'], self.logger.exception, sError)
docs: API to list data types known to dbs (when no parameter supplied).
  
          :param dataset: Returns data type (of primary dataset) of the dataset (Optional)
          :type dataset: str
          :param datatype: List specific data type
          :type datatype: str
          :returns: List of dictionaries containing the following keys (primary_ds_type_id, data_type)
          :rtype: list of dicts