@SuppressWarnings("unchecked")
    @Override
    public List<Traversal.Admin<?, ?>> getLocalChildren() {
        return Arrays.asList(
                this.targetVertexFilter.get(),
                this.edgeTraversal.get(),
                this.distanceTraversal.get());
    }
@author Daniel Kuppitz (http://gremlin.guru)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/traversal/step/map/ShortestPathVertexProgramStep.java