public List<T> getObjectsAtDepth(final int depth) {
        final List<T> list = new ArrayList<T>();
        for (final Tree<T> t : this.getTreesAtDepth(depth)) {
            list.addAll(t.keySet());
        }
        return list;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/util/Tree.java