@Override
    public void clear() {
        index.clear();
        super.clear();
    }
A {@link TraverserSet} that has an index back to the object in the {@link Traverser}. Using this extension of
{@link TraverserSet} can make it easier to find traversers within the set if the internal value is known. Without
the index the entire {@link TraverserSet} needs to be iterated to find a particular value.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/traverser/util/IndexedTraverserSet.java