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