@Override
        protected Iterator<Vertex> flatMap(final Traverser.Admin<Vertex> traverser) {
            List<Vertex> l = new ArrayList<>();
            l.add(traverser.get());
            return l.iterator();
        }
ProfileStrategy callback test. Goal: ensure that a step that implements Profileable gets a callback to setMetrics
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/ProfileTest.java