@Override
    public Set<TraverserRequirement> getRequirements() {
        return this.getSelfAndChildRequirements(
                TraverserRequirement.OBJECT,
                TraverserRequirement.SIDE_EFFECTS,
                TraverserRequirement.PATH);
    }
@author Daniel Kuppitz (http://gremlin.guru)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/TraversalSelectStep.java