@Override
    public int hashCode() {
        int result = super.hashCode();
        if (outVTraversal != null)
            result ^= outVTraversal.hashCode();
        if (inVTraversal != null)
            result ^= inVTraversal.hashCode();
        return result;
    }
Gets the traversal that will be used to provide the {@code Map} that will be used to identify the Direction.IN
vertex during merge.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/MergeEdgeStep.java