public Builder edges(final Traversal.Admin<Vertex, Edge> edgeTraversal) {
            PureTraversal.storeState(this.configuration, EDGE_TRAVERSAL, edgeTraversal);
            return this;
        }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/ranking/pagerank/PageRankVertexProgram.java