Comment tree model

models.py

class Comment(models.Model):
    """
    Representa los comentarios a los posts del blog
    """
    post = models.ForeignKey(
        'blog.Post',
    )
    user = models.ForeignKey(
        'auth.User',
    )

    comment = models.TextField(
        verbose_name="Comentario",
    )

    created_at = models.DateTimeField(
        auto_now_add=True,
    )

    parent = models.ForeignKey(
        'blog.Comment',
        null=True,
        blank=True,
        related_name='children',
    )

    def __unicode__(self):
        return u'{0}'.format(self.comment)

    class Meta:
        ordering = ['-created_at']
        verbose_name = 'Comentario'
        verbose_name_plural = 'Comentarios'