How to annotate all the objects with a new property?
class Author(Model):
    state = models.CharField('ST')

class Essay(Model):
    authors = models.ManyToManyField("Author",
        through='EssayAuthor')

>> mylist
[ <Essay: A1>, <Essay: B4>, <Essay: C9>, <Essay: A3> ... ]

>> essay0 = mylist[0]
>> essay0.state
'AK'

class Essay(Model):
    authors = models.ManyToManyField("Author",
        through='EssayAuthor')

    @property
    def state(self):
        if self.authors.count():
            return self.authors[0].state
        else:
            return null