def METHOD_NAME(self, service):
    """Check that no library ended up with multiple MARC export integrations."""
    for library in service.libraries:
        marc_export_count = 0
        for integration in library.integrations:
            if integration.goal == ExternalIntegration.CATALOG_GOAL and integration.protocol == ExternalIntegration.MARC_EXPORT:
                marc_export_count += 1
                if marc_export_count > 1:
                    return MULTIPLE_SERVICES_FOR_LIBRARY.detailed(_(
                        "You tried to add a MARC export service to %(library)s, but it already has one.",
                        library=library.short_name,
                    ))