@Override
        public Traversal<Vertex, Double> get_g_V_asXaX_groupXmX_by_byXbothE_countX_barrier_selectXmX_selectXselectXaXX_byXmathX_plus_XX() {
            return g.V().as("a").group("m").by().by(__.bothE().count()).barrier().select("m").<Double>select(__.select("a")).by(__.math("_+_"));
        }
@author Marko A. Rodriguez (http://markorodriguez.com)
@author Stephen Mallette (http://stephen.genoprime.com)
@author Daniel Kuppitz (http://gremlin.guru)
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/SelectTest.java