django-rest-framework/rest_framework/tests/models.py

from django.db import models
from django.contrib.auth.models import Group

class CustomUser(models.Model):
    """
    A custom user model, which uses a 'through' table for the foreign key
    """
    username = models.CharField(max_length=255, unique=True)
    groups = models.ManyToManyField(
        to=Group, blank=True, null=True, through='UserGroupMap'
    )

    @models.permalink
    def get_absolute_url(self):
        return ('custom_user', (), {
            'pk': self.id
    })


class UserGroupMap(models.Model):
    user = models.ForeignKey(to=CustomUser)
    group = models.ForeignKey(to=Group)      
    
    @models.permalink
    def get_absolute_url(self):
        return ('user_group_map', (), {
            'pk': self.id
        })