    },
    "language_info": {
     "codemirror_mode": {
      "name": "ipython",
      "version": 2
     },
     "file_extension": ".py",
     "mimetype": "text/x-python",
     "name": "python",
     "nbconvert_exporter": "python",
 
</s> remove    "pygments_lexer": "ipython2",
   "version": "2.7.10"
 </s> add    "pygments_lexer": "ipython3",
   "version": "3.4.3" </s> remove    "display_name": "Python 2",
 </s> add    "display_name": "Python 3", </s> remove     "            if num_stacks == 0:\n",
    "                self.last_stack = None\n",
    "            else:\n",
    "                self.last_stack = self.stacks[num_stacks-1]\n",
    "        else:\n",
    "            data = self.last_stack.pop()\n",
 </s> add  </s> remove     "* Pop on a one element stack to destroy it"
 </s> add     "* Pop on a stack to destroy it" </s> remove         capacity = 2
        stacks = SetOfStacks(capacity)
 </s> add         stacks = SetOfStacks(capacity=2)
    "version": 3
    },
    "language_info": {
     "codemirror_mode": {
      "name": "ipython",
    "version": 3
     },
     "file_extension": ".py",
     "mimetype": "text/x-python",
     "name": "python",
     "nbconvert_exporter": "python",
keep keep keep keep replace keep keep keep keep keep
 Polish set of stacks solution 
stacks_queues/set_of_stacks/set_of_stacks_solution.ipynb