public Builder edgeTraversal(final Traversal<Vertex, Edge> edgeTraversal) {
            if (null == edgeTraversal) throw Graph.Exceptions.argumentCanNotBeNull("edgeTraversal");
            PureTraversal.storeState(this.configuration, EDGE_TRAVERSAL, edgeTraversal.asAdmin());
            return this;
        }
Move any valid path into the VP's memory.
@param vertex The current vertex.
@param memory The VertexProgram's memory.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/search/path/ShortestPathVertexProgram.java