from django.db import models
class TrackingModel(models.Model):
    created_at = models.DateTimeField(auto_now_add = True)
    updated_at = models.DateTimeField(auto_now = True)
    class Meta:
       abstract = True
       ordering = ('-created_at')

from django.db import models
from helpers.models import TrackingModel

class User(TrackingModel):
    pass

from django.contrib.auth.models import (PermissionMixin,BaseUserManager,AbstractBaseUser)

class User(AbstractBaseUser,PermissionMixin,BaseUserManage):
username_validator = UnicodeUsernameValidator()          // copying from PermissionMixin > AbstractUser

class MyUserManager(UserManager):
   pass