void mergeStacks$($ItemStack& lhs$,$ const ItemStack& rhs$)$;

$/**$

$*$ Append a Node.

$*$

$*$ This is the code we discussed in Review$-01$

$*$ When this method is invoked all special cases

$*$ have already been covered in $`$addItems$`.$

$*$

$*$ Abstraction and Interfaces

$*/$