protected Traverser.Admin<E> prepareTraversalForNextStep(final Traverser.Admin<E> traverser) {
        if (!this.traverserStepIdAndLabelsSetByChild) {
            traverser.setStepId(this.nextStep.getId());
            traverser.addLabels(this.labels);
        }
        return traverser;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/util/AbstractStep.java