Fixed #21951 -- Updated docs to use __str__ for Python 3

   a field that's similar to what you want and extend it a little bit,

   instead of creating an entirely new field from scratch.

2. Put a ``__str__()`` or ``__unicode__()`` method on the class you're

2. Put a ``__str__()`` (``__unicode__()`` on Python 2) method on the class you're

   wrapping up as a field. There are a lot of places where the default

   behavior of the field code is to call

   :func:`~django.utils.encoding.force_text` on the value. (In our

   examples in this document, ``value`` would be a ``Hand`` instance, not a

   ``HandField``). So if your ``__unicode__()`` method (``__str__()`` on

   Python 3) automatically converts to the string form of your Python object,

   ``HandField``). So if your ``__str__()`` method (``__unicode__()`` on

   Python 2) automatically converts to the string form of your Python object,

   you can save yourself a lot of work.

    >>> from polls.models import Question, Choice

    # Make sure our __unicode__() addition worked.

    # Make sure our __str__() addition worked.

    >>> Question.objects.all()

    [<Question: What's up?>]

        body = models.TextField()

        status = models.CharField(max_length=1, choices=STATUS_CHOICES)

        # On Python 3: def __str__(self):

        def __unicode__(self):

        def __str__(self):              # __unicode__ on Python 2

            return self.title

A common task we might perform with a model like this is to update an

        list_display = ('first_name', 'last_name')

    If you don't set ``list_display``, the admin site will display a single

    column that displays the ``__unicode__()`` (``__str__()`` on Python 3)

    column that displays the ``__str__()`` (``__unicode__()`` on Python 2)

    representation of each object.

    You have four possible values that can be used in ``list_display``:

    A few special cases to note about ``list_display``:

    * If the field is a ``ForeignKey``, Django will display the

      ``__unicode__()`` (``__str__()`` on Python 3) of the related object.

      ``__str__()`` (``__unicode__()`` on Python 2) of the related object.

    * ``ManyToManyField`` fields aren't supported, because that would

      entail executing a separate SQL statement for each row in the table.

              list_display = ('name', 'born_in_fifties')

    * The ``__str__()`` and ``__unicode__()`` methods are just as valid in

      ``list_display`` as any other model method, so it's perfectly OK to

      do this::

    * The ``__str__()`` (``__unicode__()`` on Python 2) method is just

      as valid in ``list_display`` as any other model method, so it's

      perfectly OK to do this::

          list_display = ('__unicode__', 'some_other_field')

          list_display = ('__str__', 'some_other_field')

    * Usually, elements of ``list_display`` that aren't actual database

      fields can't be used in sorting (because Django does all the sorting

        object_id = models.PositiveIntegerField()

        content_object = GenericForeignKey('content_type', 'object_id')

        # On Python 3: def __str__(self):

        def __unicode__(self):

        def __str__(self):              # __unicode__ on Python 2

            return self.tag

A normal :class:`~django.db.models.ForeignKey` can only "point