old_contents: from django.db import models
  from django.utils.translation import gettext_lazy as _
  
  from i18nfield.fields import I18nCharField, I18nTextField
  
  
  class Author(models.Model):
      name = models.CharField(verbose_name=_('Name'), max_length=190)
  
      def __str__(self):
          return self.name
  
  
  class Book(models.Model):
      title = I18nCharField(verbose_name='Book title', max_length=190)
      abstract = I18nTextField(verbose_name='Abstract')
      author = models.ForeignKey(Author, verbose_name='Author')
  
      def __str__(self):
          return str(self.title)
  
new_contents: from django.db import models
  from django.utils.translation import gettext_lazy as _
  
  from i18nfield.fields import I18nCharField, I18nTextField
  
  
  class Author(models.Model):
      name = models.CharField(verbose_name=_('Name'), max_length=190)
  
      def __str__(self):
          return self.name
  
  
  class Book(models.Model):
      title = I18nCharField(verbose_name='Book title', max_length=190)
      abstract = I18nTextField(verbose_name='Abstract')
      author = models.ForeignKey(Author, verbose_name='Author', on_delete=models.PROTECT)
  
      def __str__(self):
          return str(self.title)
  
subject: allow demoproject to run in django 2.0+ (#33)