There is also support for a difference viewer that highlights cells in

the notebook that were modified/added/deleted.
This was used as a reference for the format of .ipynb files:

https://github.com/jupyter/nbformat/blob/master/nbformat/v4/nbformat.v4.schema.json

1) I ran unit tests with Python2.7 and Python3.6

2) I tested viewing a file normally with both Python2.7 and Python3.6

3) I tested viewing revisions of a file in the difference viewer with both

Python2.7 and Python 3.6