class UserComment(models.Model):
    sender = models.ForeignKey(User, related_name='sender',
        related_query_name='s')
recipient = models.ForeignKey(User, related_name='recipient',
    related_query_name='r')
sent_at = models.DateTimeField(auto_now_add=True)
comment = models.TextField()
How to show the last message of each user to user conversations to keep a chat history?