public void checkValid() {
            if (attribute == null) {
                throw new IllegalArgumentException("match-phase did not set any attribute");
            }
            if (! (maxHits > 0)) {
                throw new IllegalArgumentException("match-phase did not set max-hits > 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