@Nonnull
        public Builder bind(@Nonnull ClickType type, @Nullable Runnable handler) {
            Objects.requireNonNull(type, "type");
            if (handler != null) {
                this.handlers.put(type, transformRunnable(handler));
            } else {
                this.handlers.remove(type);
            }
            return this;
        }
Aids creation of {@link Item} instances.
helper/src/main/java/me/lucko/helper/menu/Item.java