title: Error when adding edges to network graph: 'v_of_edge'
body: <p>I'm trying to create a network graph in NetworkX based on a defeaultdict which contains nodes and edges. When I try to add the edges, I get the following error message:</p>
  
  <blockquote>
    <p>add_edge() missing 1 required positional argument: 'v_of_edge'</p>
  </blockquote>
  
  <p>My code is as follows:</p>
  
  <pre><code>graph = { "a" : ["c"],
        "b" : ["c", "e"],
        "c" : ["a", "b", "d", "e"],
        "d" : ["c"],
        "e" : ["c", "b"],
        "f" : []
      } 
  
  G = nx.Graph()
  
  for k,v in graph.items():
  
      G.add_node(k)
      G.add_edge(*v)
  nx.draw()
  plt.show()
  </code></pre>
  
  <p>I know that <code>add_edge</code> takes <code>(u,v)</code> argument, where I suppose that <code>u</code> is node and <code>v</code> is the edges, so instead I tried:</p>
  
  <pre><code>G.add_edge(k,v)
  </code></pre>
  
  <p>But that resulted in a new error message saying:</p>
  
  <blockquote>
    <p>unhashable type: 'list'</p>
  </blockquote>
  
  <p>I don't know how to proceed, but it leaves me at least one question.
  In the second approach, should I somehow access each edge for a given node individually?</p>