== A note about the ordering of mixin classes

In Python, when you have a class that inherits from both a primary class
and some mixin classes (for example, if you're using the [[SocketServer
stuff http://www.python.org/doc/current/lib/module-SocketServer.html]]),
it's conventional to declare your class's inheritance list with the
primary class first:

>  class Real(primary, mixin1, mixin2):
>      ....

However, an important safety tip: *if your mixin class overrides methods
of the primary class, it has to be first*. Failure to observe this
safety tip can cause head-scratching bugs followed by head-smacking
embarrassment.

(Since I was mixing stuff in to standard types like _list_ and _tuple_
and _str_, I spent a certain amount of time wondering if the interpreter
had special direct magic for them that meant I couldn't hijack and
augment their standard behavior. I felt somewhat foolish when there
turned out to be a much simpler explanation.)