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