@Nonnull
    @Override
    public Slot setItem(@Nonnull ItemStack item) {
        Objects.requireNonNull(item, "item");
        this.gui.getHandle().setItem(this.id, item);
        return this;
    }
Sets the item in this slot

@param item the new item
@return this slot
helper/src/main/java/me/lucko/helper/menu/SimpleSlot.java