@Override
    public void apply(final Traversal.Admin<?, ?> traversal) {
        if (traversal.isRoot())
            traversal.getSideEffects().setSack(this.initialValue, this.splitOperator, this.mergeOperator);
    }
The {@code SackStrategy} is used internal to the {@code withSack()} steps of {@link TraversalSource} and is not
typically constructed directly.

@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/strategy/decoration/SackStrategy.java