Countdown from n generator.

.. literalinclude:: ../../languages/python/design_generator_countdown2.py
   :language: python
   :tab-width: 4

.. runcode:: ../../languages/python/design_generator_countdown2.py
   :language: python
   :codesite: ideone

.. seealso::

   * :python-suggest-improve:`design_generator_countdown2.py`
   * :python-better-explain:`design_generator_countdown2.rst`