@Override
    public int hashCode() {
        final int hash = super.hashCode() ^ this.parameters.hashCode();
        return (null != this.cardinality) ? (hash ^ cardinality.hashCode()) : hash;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/sideEffect/AddPropertyStep.java