private static <T extends Traversal.Admin<Vertex, Edge>> T setVertexStart(final Traversal.Admin<Vertex, Edge> incidentTraversal, final Vertex vertex) {
        incidentTraversal.addStart(incidentTraversal.getTraverserGenerator().generate(vertex,incidentTraversal.getStartStep(),1l));
        return (T) incidentTraversal;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
tinkergraph-gremlin/src/main/java/org/apache/tinkerpop/gremlin/tinkergraph/process/computer/TinkerMessenger.java