@Override
    public Set<TraverserRequirement> getRequirements() {
        final Set<TraverserRequirement> requirements = this.getSelfAndChildRequirements(TraverserRequirement.BULK);
        if (requirements.contains(TraverserRequirement.SINGLE_LOOP))
            requirements.add(TraverserRequirement.NESTED_LOOP);
        requirements.add(TraverserRequirement.SINGLE_LOOP);
        return requirements;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/branch/RepeatStep.java