old_contents: # -*- coding: utf-8 -*_
  from django.db import models
  
  from ..base import ModelTranslationBase
  from ..mixins import LinguistMixin
  
  class FooModel(models.Model, LinguistMixin):
      title = models.CharField(max_length=255)
      created_at = models.DateTimeField(auto_now_add=True)
  
  
  class FooTranslation(ModelTranslationBase):
      model = FooModel
      identifier = 'foo'
      fields = ('title', )
  
  
  class BarModel(models.Model, LinguistMixin):
      title = models.CharField(max_length=255)
  
  
  class BarTranslation(ModelTranslationBase):
      model = BarModel
      identifier = 'bar'
      fields = ('title', )
  
  
  class BadTranslation(object):
      pass
  
  
  class BadModel(object):
      pass
  
new_contents: # -*- coding: utf-8 -*_
  from django.db import models
  
  from ..base import ModelTranslationBase
  from ..mixins import LinguistMixin
  
  class FooModel(models.Model, LinguistMixin):
      title = models.CharField(max_length=255, null=True, blank=True)
      created_at = models.DateTimeField(auto_now_add=True)
  
  
  class FooTranslation(ModelTranslationBase):
      model = FooModel
      identifier = 'foo'
      fields = ('title', )
  
  
  class BarModel(models.Model, LinguistMixin):
      title = models.CharField(max_length=255, null=True, blank=True)
  
  
  class BarTranslation(ModelTranslationBase):
      model = BarModel
      identifier = 'bar'
      fields = ('title', )
  
  
  class BadTranslation(object):
      pass
  
  
  class BadModel(object):
      pass
  
subject: Update test models.