public Set<String> allFilterFields() {
        Set<String> inheritedFilterFields = uniquelyInherited(RankProfile::allFilterFields, fields -> ! fields.isEmpty(),
                                                              "filter fields").orElse(Set.of());

        if (inheritedFilterFields.isEmpty()) return Collections.unmodifiableSet(filterFields);

        Set<String> combined = new LinkedHashSet<>(inheritedFilterFields);
        combined.addAll(filterFields());
        return combined;
    }
Returns all filter fields in this profile and any profile it inherits.
config-model/src/main/java/com/yahoo/schema/RankProfile.java