code: @Deprecated
    private void checkMultiExecutorMode() {
      if (!this.azkProps.getBoolean(Constants.ConfigurationKeys.USE_MULTIPLE_EXECUTORS, false)) {
        throw new IllegalArgumentException(
            Constants.ConfigurationKeys.USE_MULTIPLE_EXECUTORS +
                " must be true. Single executor mode is not supported any more.");
      }
    }
docs: TODO Then also delete ConfigurationKeys.USE_MULTIPLE_EXECUTORS.