title: AttributeError: 'Graph' object has no attribute '_node'
body: <p>I am doing Udacity's implementing a Route Planner project, the error is showing below, I have already down-grade networkx==2.3, but still have this error, is anybody can help? </p>
  
  <pre class="lang-py prettyprint-override"><code>D:\Self Learning\Anaconda3\envs\tf2.0.0rc1\lib\site-packages\networkx\classes\reportviews.py in __init__(self, graph)
      166 
      167     def __init__(self, graph):
  --&gt; 168         self._nodes = graph._node
      169 
      170     # Mapping methods
  
  AttributeError: 'Graph' object has no attribute '_node'
  </code></pre>
  
  <pre class="lang-py prettyprint-override"><code># this is the reportviews.py __init__(self,graph)
      __slots__ = '_nodes',
  
      def __getstate__(self):
          return {'_nodes': self._nodes}
  
      def __setstate__(self, state):
          self._nodes = state['_nodes']
  
      def __init__(self, graph):
          self._nodes = graph._node     #line 168, but I don't know what wrong with it?
  
      # Mapping methods
      def __len__(self):
          return len(self._nodes)
  
      def __iter__(self):
          return iter(self._nodes)
  
      def __getitem__(self, n):
          return self._nodes[n]
  </code></pre>