private <T> Optional<T> uniquelyInherited(Function<RankProfile, T> propertyRetriever,
                                              String propertyDescription) {
        return uniquelyInherited(propertyRetriever, Objects::nonNull, propertyDescription);
    }
Returns the uniquely determined property, where non-empty is defined as non-null
config-model/src/main/java/com/yahoo/schema/RankProfile.java