docs: def do_alarm_definition_update(mc, args):
      '''Update the alarm definition.'''
      fields = {}
      fields['alarm_id'] = args.id
      fields['name'] = args.name
      fields['description'] = args.description
      fields['expression'] = args.expression
      fields['alarm_actions'] = _arg_split_patch_update(args.alarm_actions)
      fields['ok_actions'] = _arg_split_patch_update(args.ok_actions)
      fields['undetermined_actions'] = _arg_split_patch_update(args.undetermined_actions)
      if args.actions_enabled not in enabled_types:
          errmsg = ('Invalid value, not one of [' +
                    ', '.join(enabled_types) + ']')
          print(errmsg)
          return
      fields['actions_enabled'] = args.actions_enabled in ['true', 'True']
      fields['match_by'] = _arg_split_patch_update(args.match_by)
      if not _validate_severity(args.severity):
          return
      fields['severity'] = args.severity
      try:
          alarm = mc.alarm_definitions.update(**fields)
      except (osc_exc.ClientException, k_exc.HttpError) as he:
          raise osc_exc.CommandError('%s\n%s' % (he.message, he.details))
      else:
          print(jsonutils.dumps(alarm, indent=2))