@Override
    public DedupGlobalStep<S> clone() {
        final DedupGlobalStep<S> clone = (DedupGlobalStep<S>) super.clone();
        clone.duplicateSet = new HashSet<>();
        if (null != this.dedupTraversal)
            clone.dedupTraversal = this.dedupTraversal.clone();
        return clone;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/DedupGlobalStep.java