City Dancers
============

We have information about swing dancers in two dictionaries:

    - The first one, let's call it ``dni_dan_D``, associates to the DNI (:class:`str`) of a dancer, the list of the swing dances he/she likes to dance.
    
    - The second one, let's call it ``dni_D``, associates to the DNI (:class:`str`) of a dancer, a list with the personal info of the dancer, which, to make it simple, consists of two :class:`str` with the name and the city of the dancer.

For example,

    .. literalinclude:: gen_city_dancers_D-test.txt
        :language: python3
        :start-after: --input-ini
        :end-before: --input-fi
        
You are required to implement the following functions in the module :mod:`city_dancers.py` (file :file:`city_dancers.py`). Bear in mind that the fist function is 80% and the second is 20%:


Generate Dancers dict
---------------------

    .. py:function:: gen_city_dancers_D(dni_dan_D, dni_D, d)

such that **given** 

    - ``dni_dan_D`` a :class:`dict` as described above,
    - ``dni_D`` a :class:`dict` as described above,
    - ``d`` a name of a swing dance (:class:`str`),

**returns** 

    a :class:`dict` where the keys are city names that are associated to a list of the names of the dancers in that city that like to dance ``d``. In the event that a dancer in ``dni_dan_D`` that dances ``d`` does not appear in ``dni_D``, their DNI will be included in a list of DNIs associated with the ``Unknown`` key. If this case never occurs then the ``Unknown`` will not appear in the resulting dictionary.

Here is an example doctest:

.. literalinclude:: gen_city_dancers_D-test.txt
    :language: python3
    :start-after: --output-ini
    :end-before: --output-fi


You will find more tests in the :download:`gen_city_dancers_D-test.txt <gen_city_dancers_D-test.txt>` file.



Sort Dancers lists
------------------

    .. py:function:: ord_city_dancers_D(cd_D)

such that **given** a :class:`dict` ``cd_D`` as the one produced by the previous function ``gen_city_dancers_D``

**modifies** 

    ``cd_D`` such that all the lists of names of dancers are alphabetically ordered.

Here is an example doctest:

.. literalinclude:: ord_city_dancers_D-test.txt
     :language: python3


You will find more tests in the :download:`ord_city_dancers_D-test.txt <ord_city_dancers_D-test.txt>` file.