@Override
    public Step<S, ?> getStartStep() {
        return this.steps.isEmpty() ? EmptyStep.instance() : this.steps.get(0);
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/util/DefaultTraversal.java