@Override
    public int compare(final A first, final A second) {
        return this.comparator.compare(this.function.apply(first), this.function.apply(second));
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/util/FunctionComparator.java