Shopping (3 points)
===================

An Italian pasta company offers caterings as a service with the pasta types that they produce. The client ordering dishes has provided a dictionary with the desired recipe names as key string (:py:class:`str`) and the associated value is a nested list of the
recipes’ ingredients: for each ingredient its name (:py:class:`str`) and units (:py:class:`float`) as sublist is provided.

Write function :py:func:`shopping()` that takes the dictionary with the defined format and a list of pasta names (:py:class:`str`) of each type produced by the company. The function returns another dictionary where the keys are the ingredient names (:py:class:`str`) and the values are the total number of units (:py:class:`int`) needed of that ingredient to cover all requested recipes. Any pasta type that is produced by the company shall not be included in this returned dictionary.

For simplicity, all units are considered the same: no conversions are needed among them.
    
Save this function to file ``p1.py``.

Examples:

.. literalinclude:: test-shopping.txt
      :language: python
      :lines: 3-11

.. note::

   More tests are provided in file :download:`test-shopping.txt`.