@Override
    public GraphComputer.Persist getPreferredPersist() {
        return GraphComputer.Persist.VERTEX_PROPERTIES;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/clustering/peerpressure/PeerPressureVertexProgram.java