from django.db import models

class A1(models.Model):

    pass

class A2(models.Model):

    pass

class A3(models.Model):

    b2 = models.ForeignKey("lookuperror_b.B2", models.CASCADE)

    c2 = models.ForeignKey("lookuperror_c.C2", models.CASCADE)

class A4(models.Model):

    pass