Fixed #18145 -- Improved documentation of unique_together type fields

        unique_together = (("driver", "restaurant"),)

    This is a list of lists of fields that must be unique when considered together.

    This is a tuple of tuples that must be unique when considered together.

    It's used in the Django admin and is enforced at the database level (i.e., the

    appropriate ``UNIQUE`` statements are included in the ``CREATE TABLE``

    statement).

    For convenience, unique_together can be a single list when dealing with a single

    For convenience, unique_together can be a single tuple when dealing with a single

    set of fields::

        unique_together = ("driver", "restaurant")