      "    * Yes\n",
      "* If we try to delete a node that doesn't exist, do we just do nothing?\n",
      "    * Yes\n",
      "* Can we assume the inputs are valid?\n",
      "    * Yes\n",
      "* Can we assume this fits memory?\n",
      "    * Yes"
     ]
 
</s> remove    "version": "3.5.0"
 </s> add    "version": "3.4.3" </s> remove    "version": "3.5.0"
 </s> add    "version": "3.4.3"
    "* Can we assume this is a connected graph?\n",
    "    * Yes\n",
      "    * Yes\n",
      "* If we try to delete a node that doesn't exist, do we just do nothing?\n",
      "    * Yes\n",
    "* Can we assume this is a connected graph?\n",
    "    * Yes\n",
      "* Can we assume the inputs are valid?\n",
      "    * Yes\n",
      "* Can we assume this fits memory?\n",
      "    * Yes"
     ]
keep keep add keep keep keep keep keep
 Update graphs challenges to add connected constraint (#151) 
graphs_trees/graph/graph_challenge.ipynb