public ItemStack transferStackInSlot(@Nonnull PlayerEntity playerIn, int index) {
        ItemStack itemstack = ItemStack.EMPTY;
        Slot slot = this.inventorySlots.get(index);
        if (slot != null && slot.getHasStack()) {
            ItemStack itemstack1 = slot.getStack();
            itemstack = itemstack1.copy();

            if (index <= 1) {
                if (!this.mergeItemStack(itemstack1, 2, inventorySlots.size(), true)) {
                    return ItemStack.EMPTY;
                }
            } else if (!this.mergeItemStack(itemstack1, 0, 2, false)) {
                return ItemStack.EMPTY;
            }

            if (itemstack1.isEmpty()) {
                slot.putStack(ItemStack.EMPTY);
            } else {
                slot.onSlotChanged();
            }
        }
        return itemstack;
    }