@Override
    public List<Pair<Traversal.Admin<S, C>, Comparator<C>>> getComparators() {
        return this.comparators.isEmpty() ? Collections.singletonList(new Pair<>(new IdentityTraversal(), (Comparator) Order.asc)) : Collections.unmodifiableList(this.comparators);
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/OrderGlobalStep.java