@Override
        public void map(final Vertex vertex, final MapEmitter<Integer, Integer> emitter) {
            vertex.<Integer>property("age").ifPresent(age -> emitter.emit(age, age));
        }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/process/computer/GraphComputerTest.java