@Override
    public Set<Class<? extends OptimizationStrategy>> applyPrior() {
        return PRIORS;
    }
Determines if the strategy should be applied or not. It returns {@code true} and is "not applicable" when the
following conditions are met:
<ul>
    <li>If there are lambdas as you can't introspect to know what path information the lambdas are using</li>
    <li>If a PATH requirement step is being used (in the future, we can do PATH requirement lookhead to be more intelligent about its usage)</li>
    <li>If a VertexProgramStep is present with LABELED_PATH requirements</li>
</ul>
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/strategy/optimization/PathRetractionStrategy.java