from django.db import models

class Poll(models.Model):

    question = models.CharField(max_length=200)

class Choice(models.Model):

    poll = models.ForeignKey(Poll, models.CASCADE)

    choice = models.CharField(max_length=200)

# 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, models.CASCADE)

    # second would clash with the __second lookup.

    third = models.ForeignKey(OuterB, models.SET_NULL, null=True)