public default Set<TraverserRequirement> getTraverserRequirements() {
        return Collections.emptySet();
    }
The traverser requirements that are needed when this VP is used as part of a traversal.
The default is an empty set.

@return the traverser requirements
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/VertexProgram.java