https://scikit-learn.org/stable/auto_examples/tree/plot_iris_dtc.html

Note: I tried fixing it quickly by playing with the figsize to no avail. Looks like you can see the full diagram on the matplotlib figure but the diagram is cropped when saving to a png.

Looks like it was working fine in 0.24 (maybe a regression or maybe some changes in matplotlib hard to tell ...):
https://scikit-learn.org/0.24/auto_examples/tree/plot_iris_dtc.html