The Django "Model Meta options" docs provide examples and generally
point the reader to use lists for the unique_together and ordering
options. Follow our own advice for contrib models.
More generally, lists should be used for homogeneous sequences of
arbitrary lengths of which both unique_together and ordering are.
Jon Dufresne
Claude Paroz
Dražen Odobašić
Piotr Jakimiak
Tim Graham
Markus Holtermann