public Builder target(final Traversal<Vertex, ?> targetVertexFilter) {
            if (null == targetVertexFilter) throw Graph.Exceptions.argumentCanNotBeNull("targetVertexFilter");
            PureTraversal.storeState(this.configuration, TARGET_VERTEX_FILTER, targetVertexFilter.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