@Override
    protected Traverser.Admin<E> processNextStart() {
        while (true) {
            if (this.iterator.hasNext()) {
                return this.isStart ? this.getTraversal().getTraverserGenerator().generate(this.iterator.next(), (Step) this, 1l) : this.head.split(this.iterator.next(), this);
            } else {
                if (this.isStart) {
                    if (this.done)
                        throw FastNoSuchElementException.instance();
                    else {
                        this.done = true;
                        this.iterator = null == this.iteratorSupplier ? EmptyIterator.instance() : this.iteratorSupplier.get();
                    }
                } else {
                    this.head = this.starts.next();
                    this.iterator = null == this.iteratorSupplier ? EmptyIterator.instance() : this.iteratorSupplier.get();
                }
            }
        }
    }
Gets the ids associated with this step as literal values rather than {@link GValue} objects.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/GraphStep.java