@Override
    protected Iterator<E> flatMap(final Traverser.Admin<S> traverser) {
        return this.function.apply(traverser);
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/LambdaFlatMapStep.java