title: Possible to modify/prune learned trees in scikit-learn?
body: <p>It is possible to access tree parameters in sklearn with</p>
  
  <pre><code>tree.tree_.children_left
  tree.tree_.children_right
  tree.tree_.threshold
  tree.tree_.feature
  </code></pre>
  
  <p>and so on</p>
  
  <p>However, trying to write to these variables raises a not writable exception</p>
  
  <p>Is there any way to modify the learned tree, or bypass the AttributeError not writable?</p>