class Post(models.Model):
    title = models.CharField(max_length=200)
    slug = models.CharField(max_length=200)


class ItemBase(models.Model):
    #post = models.ManyToManyField('Post', related_name='%(class)s_related')
    title = models.CharField(max_length=250)

    class Meta:
        abstract = True

    def render(self):
        return render_to_string('content/items/{}.html'.format(self._meta.model_name), {'item': self})


class Image(ItemBase):
    image_url = models.URLField(blank=True, null=True)
    image_file = models.ImageField(upload_to='posts/%Y/%m/%d',
                                   blank=True, null=True)