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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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)