title: legend in python networkx
body: <p>I have the following code to draw a graph with nodes but i am failing to add a proper legend:
  (sorry, i can't post an image it seems i don't have enough reputation)</p>
  
  <p>I want a legend with the 4 colors, such as "light blue = obsolese, red = Draft, Yellow = realease, dark blue = init".</p>
  
  <p>I have seen some solutions with "scatter" but i think it is too complicated. Is there a way to do it with <code>plt.legend(G.nodes)</code>?</p>
  
  <p>Here is the code:</p>
  
  <pre><code>import networkx as nx
  import matplotlib.pyplot as plt
  import numpy as np
  G=nx.Graph()
  G.add_node("kind1")
  G.add_node("kind2")
  G.add_node("Obsolete")
  G.add_node("Draft")
  G.add_node("Release")
  G.add_node("Initialisation")
  val_map = {'kind1': 2,'kind2': 2,'Obsolete': 2,'Initialisation': 1,'Draft': 4,'Release': 3}
  values = [val_map.get(node, 0) for node in G.nodes()]
  nodes = nx.draw(G, cmap = plt.get_cmap('jet'), node_color = values)
  
  plt.legend(G.nodes())
  plt.show() 
  </code></pre>