title: 'DecisionTreeClassifier' object has no attribute 'export_graphviz'
body: <p>I'm using python sklearn RandomForestClassifier and try to export decisiontrees.</p>
  
  <p>The basic code is as following:</p>
  
  <pre><code>from sklearn import tree
  
  with open(dot_file_name, 'w') as my_file:
      tree.export_graphviz(tree1, out_file = my_file,feature_names = feature_names)
  </code></pre>
  
  <p>After run the python script, following error show up:
  Attribute error: 'DecisionTreeClassifier' object has no attribute 'export_graphviz'</p>
  
  <p>I'm using python 2.7. Is it because of the version of python? Do I have to use python 3.0?</p>