Model mixins are abstract classes that can be added as a parent class of a model. Python supports multiple inheritances, unlike other languages such as Java. Hence, you can list any number of parent classes for a model.
Mixins ought to be orthogonal and easily composable. Drop in a mixin to the list of base classes and they should work. In this regard, they are more similar in behavior to composition rather than inheritance.
Smaller mixins are better. Whenever a mixin becomes large and violates the single responsibility principle, consider refactoring it into smaller classes. Let a mixin do one thing and do it well.
In our previous example, the model mixin used to update created and modified time can be easily factored out, as ...
