code: def iter_services(self, service_group=None):
      
      if service_group is not None:
        if service_group not in EFConfig.SERVICE_GROUPS:
          raise RuntimeError("service registry: {} doesn't have '{}' section listed in EFConfig".format(
            self._service_registry_file, service_group))
        return self.service_registry_json[service_group].iteritems()
      else:
       return self.services().iteritems()
docs: Args:
        service_group: optional name of service group
      Returns:
        if service_group is omitted or None, an Iterator over all flattened service records in the service registry
        if service_group is present, an Iterator over all service records in that group