@Override
        default Service createService(final boolean isStart, final Map params) {
            if (!isStart) {
                throw new UnsupportedOperationException(Exceptions.directoryStartOnly);
            }
            return this;
        }
Meta-service to list and describe registered callable services.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/structure/service/Service.java