public default Traverser.Admin<E> nextTraverser() {
            return this.getEndStep().next();
        }
Gets the {@link TraversalSource} that spawned the {@link Traversal} instance initially if present. This
{@link TraversalSource} should have spawned from the associated {@link Graph} returned from
{@link #getGraph()}.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/Traversal.java