private void traverseHighlight(Highlight highlight, IndexFacts.Session indexFacts) {
        if (highlight == null) return;

        for (AndItem item : highlight.getHighlightItems().values()) {
            traverse(item, indexFacts);
        }
    }
Traverse a query tree and lowercase terms based on decision made in subclasses.

@author Steinar Knutsen
container-search/src/main/java/com/yahoo/search/querytransform/LowercasingSearcher.java