advanced mathematical feature. If you're not aware of a need for them,
it's almost certain you can safely ignore them.
+ context manager
+ Objects which control the environment seen in a :keyword:`with`
+ statement by defining :meth:`__enter__` and :meth:`__exit__` methods.
+ See :pep:`343`.
+
decorator
A function returning another function, usually applied as a function
transformation using the ``@wrapper`` syntax. Common examples for