fun setItems(holder: PersistentDataHolder, key: NamespacedKey, items: List<ItemStack?>?) Stores a list of items (Base64) under key; null removes the key.
fun setItems(item: ItemStack, key: NamespacedKey, items: List<ItemStack?>?): ItemStack Stores a list of items (Base64) under key on an item; null removes it. Returns the stack.