title: How to get nodes coordinates in graph rendered with graphviz
body: <p>I'm implementing a stepwise graph transformation algorithm where nodes are removed or added in each step and want to keep a trace of all the intermediate graphs as images files where a node keeps rendered at the same position until removed. This will help make a final animation.</p>
  
  <p>I thought about getting the nodes positions from the initial step as computed by the layout engine and then pass them as a node attribute for next steps.</p>
  
  <p>I'm using the graphviz library, but I could not find any way to get the nodes coordinates (<code>pos</code> attribute) in the rendered graphs. Here is a code excerpt. </p>
  
  <pre class="lang-py prettyprint-override"><code>    from graphviz import Digraph
      dot = Digraph()
      dot.node('x', label='hello')
      dot.node('y', label='world')
      dot.edge('x', 'y')
      dot.render(filename='hello.gv', view=True, cleanup=False)
  </code></pre>
  
  <p>I also inspected the <code>dot</code> object, but found nothing. Am I missing some thing? I could not conform whether positions are exported via the API or no. In this case, which different library can help?</p>