from django.db import models

from django.utils import timezone

class RelatedModel(models.Model):

    simple = models.ForeignKey("SimpleModel", models.CASCADE, null=True)

class SimpleModel(models.Model):

    field = models.IntegerField()

    created = models.DateTimeField(default=timezone.now)

class ManyToManyModel(models.Model):

    simples = models.ManyToManyField("SimpleModel")