@Override
    protected Vertex map(final Traverser.Admin<S> traverser) {
        final Vertex vertex = this.getTraversal().getGraph().get().addVertex(this.parameters.getKeyValues(traverser));
        EventUtil.registerVertexCreation(callbackRegistry, getTraversal(), vertex);
        return vertex;
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/AddVertexStep.java