@Override
        public Traversal<Vertex, Map<String, Collection<Vertex>>> get_g_V_group_byXnameX_by() {
            return g.V().<String, Collection<Vertex>>group().by("name").by();
        }
@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