private void addIndexSettings(ImmutableSDField field, RankSetting.Type type, Set<RankSetting> settings) {
        String indexName = field.getName();

        // TODO: Make a ranking object in the index override the field level ranking object
        if (type.equals(RankSetting.Type.PREFERBITVECTOR) && field.getRanking().isFilter()) {
            settings.add(new RankSetting(indexName, type, true));
        }
    }
Returns the names of the fields which have a rank boost setting
explicitly in this profile or in fields
config-model/src/main/java/com/yahoo/schema/DefaultRankProfile.java