@Override
        public void setStoredValue(String value) {
            if (value == null || value.isEmpty()) {
                this.value = null;
            } else {
                this.value = value.toLowerCase(Locale.ROOT);
            }
        }
Simple implementation which just holds a stored value.
common/src/main/java/me/lucko/luckperms/common/model/PrimaryGroupHolder.java