public void addRankSetting(String fieldName, RankSetting.Type type, Object value) {
        addRankSetting(new RankSetting(fieldName, type, value));
    }
Returns the property retrieved by the given function, if it is only present in a single unique variant
among all profiled inherited by this, or empty if not present.
Note that for properties that don't implement a values-based equals this reverts to the stricter condition that
only one inherited profile can define a non-empty value at all.

@throws IllegalArgumentException if the inherited profiles defines multiple different values of the property
config-model/src/main/java/com/yahoo/schema/RankProfile.java