title: Attribute error using Pydot to create a graph
body: <p>I am using IPython on Windows10 to train and draw out a decision tree. I know the following code worked on linux some time back. I installed pydot and also have graphviz (with the path correctly specified). </p>
  
  <pre><code># Train and draw out a decision tree
  
  from IPython import display
  from sklearn import datasets, tree, utils
  from sklearn.externals.six import StringIO  
  import pydot 
  
  # Train a small decision tree on the iris dataset
  dataset = datasets.load_iris()
  X_iris, y_iris = utils.shuffle(dataset.data, dataset.target,random_state=42)
  tree_clf = tree.DecisionTreeClassifier(max_depth=3).fit(X_iris, y_iris)
  
  # Generate a plot of the decision tree
  dot_data = StringIO() 
  tree.export_graphviz(tree_clf, out_file=dot_data) 
  graph = pydot.graph_from_dot_data(dot_data.getvalue()) 
  display.Image(graph.create_png())
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>---------------------------------------------------------------------------
  AttributeError                            Traceback (most recent call last)
  &lt;ipython-input-5-3452aa5e9794&gt; in &lt;module&gt;()
       15 tree.export_graphviz(tree_clf, out_file=dot_data)
       16 graph = pydot.graph_from_dot_data(dot_data.getvalue())
  ---&gt; 17 display.Image(graph.create_png())
  
  AttributeError: 'list' object has no attribute 'create_png'
  </code></pre>