@Override
        public Traversal<Vertex, Map<String, Number>> get_g_V_hasLabelXpersonX_asXpX_outXcreatedX_group_byXnameX_byXselectXpX_valuesXageX_sumX() {
            return g.V().hasLabel("person").as("p").out("created").<String, Number>group().by("name").by(__.select("p").values("age").sum());
        }
@author Marko A. Rodriguez (http://markorodriguez.com)
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/sideEffect/GroupTest.java