@Override
    public void addBarrier(final TraverserSet<S> barrier) {
        IteratorUtils.removeOnNext(barrier.iterator()).forEachRemaining(traverser -> {
            traverser.setSideEffects(this.getTraversal().getSideEffects());
            this.addStart(traverser);
        });
    }
@author Matt Frantz (http://github.com/mhfrantz)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/TailGlobalStep.java