Yeah ordered_dict was removed as it's part of the python stdlib now. I didn't realize you would be using that as it has existed in the stdlib for a while. I tend to forget that not everyone is as immersed in python as I am
Other cleanups are adding the header:
from __future__ import (unicode_literals, division, absolute_import,
print_function)
to all new code in calibre, this mostly is for python 3 compatibility.
The replacing of __import__ with importlib.import_module and trying to remember to use
from future_builtins import map
wherever I use the map builtin.
Apart from ordered_dicts nonoe of the other changes should matter to you unless you want to get the plugin included into the calibre codebase.