      "* Is the graph directed?\n",
      "    * Yes\n",
      "* Can we assume we already have Graph and Node classes?\n",
      "    * Yes"
     ]
    },
    {
     "cell_type": "markdown",
 
</s> remove     "version": 2
 </s> add     "version": 3 </s> remove     "version": 2
 </s> add     "version": 3
    "    * Yes\n",
    "* Can we assume the inputs are valid?\n",
    "    * Yes\n",
    "* Can we assume this fits memory?\n",
      "* Is the graph directed?\n",
      "    * Yes\n",
      "* Can we assume we already have Graph and Node classes?\n",
    "    * Yes\n",
    "* Can we assume the inputs are valid?\n",
    "    * Yes\n",
    "* Can we assume this fits memory?\n",
      "    * Yes"
     ]
    },
    {
     "cell_type": "markdown",
keep keep add keep keep keep keep keep
 Update constraints for bfs and dfs graph challenge and solution (#88) 
graphs_trees/graph_dfs/dfs_solution.ipynb