code: protected Boolean getBooleanParam(String paramName, String errorMessage) throws IOException {
          return getBooleanParam(paramName, errorMessage, (Map<String, Object>) inputParams.get());
      }
docs: Convenience method for subclasses.
  
  @param paramName    the name of the parameter
  @param errorMessage the errormessage to add to the exception if the param does not exist.
  @return a stringparameter with given name. If it does not exist and the errormessage is provided,
  an IOException is thrown with that message. if the errormessage is not provided, null is returned.
  @throws IOException Exception if the paramname does not exist and an errormessage is provided.