list_display - boolean icons for methods

Question

This is documented, although it's a bit hard to find - go a couple of screens down from here, and you'll find this:

If the string given is a method of the model, ModelAdmin or a callable that returns True or False Django will display a pretty "on" or "off" icon if you give the method a boolean attribute whose value is True.

and the example given is:

def born_in_fifties(self):
    return self.birthday.strftime('%Y')[:3] == '195'
born_in_fifties.boolean = True

Thanks to @daniel-roseman (rtfm)
Since Django 3.2 there is a decorator @admin.display(boolean=True):

If the string (in list_display) given is a method of the model, ModelAdmin or a callable that returns True, False, or None, Django will display a pretty “yes”, “no”, or “unknown” icon if you wrap the method with the display() decorator passing the boolean argument with the value set to True:

class Person(models.Model):
    birthday = models.DateField()

    @admin.display(boolean=True)
    def born_in_fifties(self):
        return 1950 <= self.birthday.year < 1960