Visualizing decision trees in scikit-learn

For single decision trees:

http://scikit-learn.org/dev/modules/tree.html

http://stackoverflow.com/questions/10570042/visualizing-a-decision-tree-example-from-scikit-learn

Hints on how to do it for a Random Forest or Extra Tree classifier:

http://stackoverflow.com/questions/17057139/how-to-find-key-trees-features-from-a-trained-random-forest

http://stackoverflow.com/questions/17362576/random-forest-implementation-in-python