Bikes
=====

Let's consider a given dictionary where the key is an :class:`int` with a person's *ID number* and the value is a :class:`str` with the name of her/his city of residence. For example:

.. literalinclude:: bikeD_gen.test
    :language: python3
    :start-after: --ini1
    :end-before: --fi1

In this context, you are required to deliver the following functions in the module :mod:`bikes` (file :file:`bikes.py`):

------------------------------------------------------------------------------------------------

The first function is:

    .. py:function:: bikeD_gen(id_city_D, id_bike_D)

such that

    **given**

    - *id_city_D*, is a :class:`dict` as described above
    - *id_bike_D*, is a :class:`dict` where the key is a :class:`int` with a person's *ID number* and the corresponding value is a :class:`str` with the brand of his/her **motor bike**.

    **returns** a :class:`dict` with the inverted info of *id_bike_D* but only with the persons included in *id_city_D*. Specifically the keys of the new dict are bike brands appearing as values in *id_bike_D*  and the value corresponding to each key is a :class:`list` of Id numbers, the ones that who appear in *id_city_D* and own a bike of that brand according to *id_bike_D*. The order of these lists is the same as in the input dictionary.

For example:

    .. literalinclude:: bikeD_gen.test
        :language: python3
        :start-after: --ini2
        :end-before: --fi2

Observe that the id ``77888999`` is not listed in ``'Ducati``'s value because it is not a key in ``id_city_d``.

Doctests are available in the :download:`bikeD_gen.test` file.

------------------------------------------------------------------------------------------------

Now let's consider the case where a person can own more that one bike.
Hence we have the dictionary *id_bikes_D* where the key is a :class:`int` with a person's *ID number*
and the associated value is a :class:`list` of :class:`str` with the brands of the *motor bikes* owned by that person.

For example:

.. literalinclude:: cityD_gen.test
    :language: python3
    :start-after: --ini1
    :end-before: --fi1

The second function is:

    .. py:function:: cityD_gen(id_city_D, id_bikes_D, brd)

such that

    **given**

    - *id_city_D*, is a :class:`dict` as described at the beginning
    - *id_bikes_D*, is a :class:`dict` as described above
    - *brd*, a :class:`str` with a motor bike brand name

    **returns** a :class:`dict` with all *Idn*s in *id_city_D* that own a motorbike whose brand is *brd*.
    The key is a :class:`str` with a city of residence according to *id_city_D* and
    the associated value is an **aphabetically ordered** :class:`list` of those person's Idn (:class:`int`).
    The owners of a bike of brand *brd* in *id_bikes_D* that do not appear in *id_city_D* must be listed under the ``'Unknown'`` key.

    Notice that the cities where there is no bike owner of this brand are not included in the dictionary's keys.

    For instance, observe the following example:
    in the first call, the Id ``77888999`` is listed under the ``'Unknown'`` since it belongs to somebody who owns a Ducati but is not included in *id_city_D*.
    Furthermore, in the second call, all Ducati owners are listed under the ``'Unknown'`` key since the *id_city_D* provided is empty.

For example:

    .. literalinclude:: cityD_gen.test
        :language: python3
        :start-after: --ini2
        :end-before: --fi2

Observe that the second example, all  ``'Ducati`` owners are listed in the  ``Unknown`` key since the is the is empty.

Doctests are available in the :download:`cityD_gen.test` file.