private static void registerTrait() {
        if (CitizensAPI.getTraitFactory().getTrait(ClickableTrait.class) == null) {
            try {
                CitizensAPI.getTraitFactory().registerTrait(TraitInfo.create(ClickableTrait.class));
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
Implementation of {@link NpcFactory} using Citizens.
helper/src/main/java/me/lucko/helper/npc/CitizensNpcFactory.java