public Traversal.Admin<S, Object> getOutVTraversal() {
        return outVTraversal;
    }
Gets the traversal that will be used to provide the {@code Map} that will be used to identify the Direction.OUT
vertex during merge.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/MergeEdgeStep.java