public default Set<TraverserRequirement> getRequirements() {
        return Collections.emptySet();
    }
Provide the necessary {@link TraverserRequirement} that must be met by the traverser in order for the step to
function properly. The provided default implements returns an empty set.

@return the set of requirements
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/Step.java