      "* Do we expect the methods to be enqueue and dequeue?\n",
      "    * Yes\n",
      "* Can we assume we already have a stack class that can be used for this problem?\n",
      "    * Yes"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
 
</s> remove     "* Do you expect the methods to be enqueue and dequeue?\n",
 </s> add     "* Do we expect the methods to be enqueue and dequeue?\n", </s> remove     "* Do you expect the methods to be enqueue and dequeue?\n",
 </s> add     "* Do we expect the methods to be enqueue and dequeue?\n", </s> remove     "        if self.right_stack.is_empty() and not self.left_stack.is_empty():\n",
    "            self.shift_stacks(self.left_stack, self.right_stack)\n",
 </s> add     "        self.shift_stacks(self.left_stack, self.right_stack)\n", </s> remove     "* If the left stack is empty and the right stack is not empty\n",
 </s> add     "* If right stack is not empty\n",
    "    * Yes\n",
    "* Can we push a None value to the Stack?\n",
    "    * No\n",
    "* Can we assume this fits memory?\n",
      "* Do we expect the methods to be enqueue and dequeue?\n",
      "    * Yes\n",
      "* Can we assume we already have a stack class that can be used for this problem?\n",
    "    * Yes\n",
    "* Can we push a None value to the Stack?\n",
    "    * No\n",
    "* Can we assume this fits memory?\n",
      "    * Yes"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
keep keep add keep keep keep keep keep keep
 Polish queue from stacks challenge and solution (#74)

Update constraints, algorithm discussion, and code. 
stacks_queues/queue_from_stacks/queue_from_stacks_challenge.ipynb