Most of the changes are related with dictionaries returning views instead of
lists.
xrange -> range (since xrange is gone in python 3)
The code that is special to support both python 2 and 3 is enclosed in a comment
\# Provide support for both python 2 and 3
and
\# End of code to support for both python 2 and 3
And so later it can be removed safely when python 2 is no longer supported.
