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