@Override
    public MathStep<S> clone() {
        final MathStep<S> clone = (MathStep<S>) super.clone();
        clone.traversalRing = this.traversalRing.clone();
        return clone;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/MathStep.java