public static Graph open(final Configuration conf) {
            return EmptyGraph.instance();
        }
{@link EmptyGraph} doesn't have a standard {@code open()} method because it is a singleton. Use this factory
to provide as a {@link GraphFactoryClass} for {@link EmptyGraph} so that {@link GraphFactory} can instantiate
it in a generalized way. End users should not generally use this method of instantiation.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/structure/util/empty/EmptyGraph.java