def alt(key):
    """Make a string that tmux will parse as the alt key (:kbd:`Alt`) and
    ``key`` pressed at the same time.

    .. note::

       The ``key`` parameter is case-sensitive. If ``key`` is uppercase, it's
       equivalent to entering :kbd:`Shift` and the key.

       .. doctest::

          >>> from oraide.keys import alt
          >>> alt('a')  # alt + a
          'A-a'
          >>> alt('A')  # alt + shift + a
          'A-A'
    """
    return 'A-{}'.format(key)
