void checkValid() {
            if (attribute == null || attribute.isEmpty()) {
                throw new IllegalArgumentException("'diversity' did not set non-empty diversity attribute name.");
            }
            if (minGroups <= 0) {
                throw new IllegalArgumentException("'diversity' did not set min-groups > 0");
            }
            if (cutoffFactor < 1.0) {
                throw new IllegalArgumentException("diversity.cutoff.factor must be larger or equal to 1.0.");
            }
        }
True if this should be inlined into calling expressions. Useful for very cheap functions.
config-model/src/main/java/com/yahoo/schema/RankProfile.java