Combine Nums
============

We wish to combine two given, non-empty, digits only, strings into a new, digits only, string.
Notice from the examples that the two given string do not necessarily have the same length.
You are required to deliver the following function in the module :mod:`nums_module` (file :file:`nums_module.py`):

    .. py:function:: nums_combine(n1, n2)

such that

    **given** *n1*, *n2* :class:`str` with non-empty, not necessarily with the same length, sequences of digits.

    **returns** a :class:`str` generated by taking the *integer part of the mean* of the digits aligned in the same position of *n1* and *n2*. In case a position is exists only in one of the strings (because the other one is shorter) then that digit is taken.

For instance, *nums_combine* of ``'111'``, ``'78901'`` should produce ``'44501'``. The first three digits correspond each to the *integer mean* of the two digits in the same position in *n1* and *n2*. Namely: 4 is the int mean of 1 and 7, 4 is also the int mean of 1 and 8, and 5 is the int mean of 1 and 9. Finally ``'01'`` is the tail of the longest one.

See more examples:

    .. literalinclude:: nums_combine.test
        :language: python3
        :start-after: --ini
        :end-before: --fi

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