@Override
    public int hashCode() {
        return super.hashCode() ^
                this.traversalRing.hashCode() ^
                Boolean.hashCode(this.isSimple) ^
                (null == this.fromLabel ? "null".hashCode() : this.fromLabel.hashCode()) ^
                (null == this.toLabel ? "null".hashCode() : this.toLabel.hashCode());
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/PathFilterStep.java