public default Set<Class<? extends S>> applyPrior() {
        return Collections.emptySet();
    }
The set of strategies that must be executed before this strategy is executed.
If there are no ordering requirements, the default implementation returns an empty set.

@return the set of strategies that must be executed prior to this one.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/TraversalStrategy.java