from django.db import models

class Poll(models.Model):

    question = models.CharField(max_length=200)

    def __unicode__(self):

        return u"Q: %s " % self.question

class Choice(models.Model):

    poll = models.ForeignKey(Poll)

    choice = models.CharField(max_length=200)

    def __unicode__(self):

        return u"Choice: %s in poll %s" % (self.choice, self.poll)

# A set of models with an inner one pointing to two outer ones.

class OuterA(models.Model):

    pass

class OuterB(models.Model):

    data = models.CharField(max_length=10)

class Inner(models.Model):

    first = models.ForeignKey(OuterA)

    second = models.ForeignKey(OuterB, null=True)