docs: def _validate_config(self):
          """Ensure at least one switch is configured"""
          if len(cfg.CONF.ml2_arista.get('switch_info')) < 1:
              msg = _('Required option - when "sec_group_support" is enabled, '
                      'at least one switch must be specified ')
              LOG.exception(msg)
              raise arista_exc.AristaConfigError(msg=msg)