@Override
    public Service<Vertex, Long> createService(final boolean isStart, final Map params) {
        if (isStart) {
            throw new UnsupportedOperationException(Service.Exceptions.cannotStartTraversal);
        }
        return this;
    }
Count the IN/OUT/BOTH edges for a set of vertices. Demonstrates a {@link Service.Type#Streaming} service.
tinkergraph-gremlin/src/main/java/org/apache/tinkerpop/gremlin/tinkergraph/services/TinkerDegreeCentralityFactory.java