      "class Graph:\n",
      "\n",
      "    def __init__(self):\n",
      "        # TODO: Implement me\n",
      "        self.nodes = OrderedDict()  # key = node id, val = node\n",
      "\n",
      "    def add_node(self, id):\n",
      "        # TODO: Implement me\n",
      "        pass\n",
      "\n",
 
</s> remove     "        self.nodes = OrderedDict()  # key = node id, val = node\n",
 </s> add     "        self.nodes = {}  # key = node id, val = node\n", </s> remove     "        self.adjacent = OrderedDict()  # key = node, val = weight\n",
 </s> add     "        self.adjacent = {}  # key = node, val = weight\n", </s> remove     "from collections import OrderedDict\n",
    "\n",
    "\n",
 </s> add 
    "        self.nodes = {}  # key = node id, val = node\n",
      "class Graph:\n",
      "\n",
      "    def __init__(self):\n",
      "        # TODO: Implement me\n",
    "        self.nodes = {}  # key = node id, val = node\n",
      "\n",
      "    def add_node(self, id):\n",
      "        # TODO: Implement me\n",
      "        pass\n",
      "\n",
keep keep keep keep replace keep keep keep keep keep
 Rework graph challenge and solution (#86) 
graphs_trees/graph/graph_challenge.ipynb