old_contents: from __future__ import unicode_literals
  
  from django.db import models
  from django.core import validators
  from django.contrib.auth.models import AbstractBaseUser
  
  # Create your models here.
  
  
  class User(AbstractBaseUser):
      uid = models.PositiveIntegerField(validators=[validators.MinValueValidator(1000)])
      gid = models.PositiveIntegerField(validators=[validators.MinValueValidator(1000)])
      username = models.CharField(max_length=32)
      superuser = models.BooleanField(default=False)
      USERNAME_FIELD = 'username'
      REQUIRED_FIELDS = ['uid, gid', 'superuser']
  
  
  class Group(models.Model):
      gid = models.PositiveIntegerField(primary_key=True, validators=[MinValueValidator(1000)])
      groupname = models.CharField(max_length=32)
      users = models.ManyToManyField(User, related_name='groups')
  
new_contents: from __future__ import unicode_literals
  
  from django.db import models
  from django.core import validators
  from django.contrib.auth.models import AbstractBaseUser
  
  # Create your models here.
  
  
  class User(AbstractBaseUser):
      uid = models.PositiveIntegerField(validators=[validators.MinValueValidator(1000)])
      gid = models.PositiveIntegerField(validators=[validators.MinValueValidator(1000)])
      username = models.CharField(max_length=32)
      superuser = models.BooleanField(default=False)
      USERNAME_FIELD = 'username'
      REQUIRED_FIELDS = ['uid, gid', 'superuser']
  
  
  class Group(models.Model):
      gid = models.PositiveIntegerField(primary_key=True, validators=[validators.MinValueValidator(1000)])
      groupname = models.CharField(max_length=32)
      users = models.ManyToManyField(User, related_name='groups')
  
subject: fix validator