@Override
        public Traversal<Integer, Double> get_g_injectXnull_10_20_nullX_mean() {
            return g.inject(null, 10, 20, null).mean();
        }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/MeanTest.java