private Set<String> fieldsAlreadyFilled(Set<String> alreadyFilled) {
        var gotFields = new HashSet<String>();
        for (var hasSummary : alreadyFilled) {
            if (hasSummary == PRESENTATION) continue;
            var hasSome = getFieldsForClass(hasSummary);
            for (String field : hasSome) {
                gotFields.add(field);
            }
        }
        return gotFields;
    }
resolve summary class to use when none provided
container-search/src/main/java/com/yahoo/prelude/fastsearch/PartialSummaryHandler.java