@Override
    public void modulateBy(final Traversal.Admin<?, ?> selectTraversal) {
        this.selectTraversal = this.integrateChild(selectTraversal);
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/SelectOneStep.java