Upper Unitari Letters
=====================

You are required to deliver the following function in the module :mod:`upper_module` (file :file:`upper_module.py`):

    .. py:function:: upper_uni(text, ref)

such that

    **given**
        - *text*, :class:`str` of characters
        - *ref*, :class:`str` of lowercase *letters*

    **returns** a :class:`str` like *text* where
        - all letters, either occurring only once or appearing in *ref*, are in **upper case**.
        - all characters that are not aphanumeric are **deleted**.

For example:

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

Observe in the resulting string that:

    - all ``'p'`` are in upper case since it appears in the string of the second parameter (*ref*),
    - ``'q'`` is also in upper case since it occurs only once,
    - all digits remain untouched
    - All spaces ``' '``, comas ``','`` dots and ``'.'`` have been removed.

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