Putting a bet to record Django model

im working on a social network project and im going to make follower and following to my users and i did it with another Model named Follow

class Follow(models.Model):
    follower = models.ForeignKey(User,on_delete=models.CASCADE,related_name="followers", blank=False,null=False)
    following = models.ForeignKey(User,on_delete=models.CASCADE,related_name="followings",blank=False,null=False)

    def __str__(self):
        return self.follower.username + " is following " + self.following.username

and now im gonna put conditions to record, for example somebody can't follow himself or if that record exists, don't record it again

Thanks for reading. Comments are Welcomed