old_contents: from django.db import models
  
  
  class License(models.Model):
      name = models.CharField(max_length=80, unique=True)
      symbols = models.CharField(max_length=5)
      url = models.URLField(unique=True)
  
      def __unicode__(self):
          return self.name
  
      def get_absolute_url(self):
          return self.url
  
  class Licensed(models.Model):
      license = models.ForeignKey(License)
      class Meta:
          abstract = True
  
  
  
new_contents: from django.db import models
  
  
  class License(models.Model):
      name = models.CharField(max_length=80, unique=True)
      symbols = models.CharField(max_length=5)
      url = models.URLField(unique=True)
  
      def __unicode__(self):
          return self.name
  
      def __str__(self):
          return self.name
  
      def get_absolute_url(self):
          return self.url
  
  class Licensed(models.Model):
      license = models.ForeignKey(License)
      class Meta:
          abstract = True
  
  
  
subject: Add __str__() method to license model