@Override
    public Computer getComputer() {
        Computer tempComputer = this.computer;
        if (!this.isEndStep()) {
            if (null == tempComputer.getPersist())
                tempComputer = tempComputer.persist(GraphComputer.Persist.EDGES);
            if (null == tempComputer.getResultGraph())
                tempComputer = tempComputer.result(GraphComputer.ResultGraph.NEW);
        }
        return tempComputer;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/traversal/step/map/VertexProgramStep.java