old_contents: from django.db import models
  
  # Represents a category which articles can be part of
  class Category(models.Model):
      name = models.CharField(max_length=255)
  
      def __str__(self):
          return self.name+" ["+str(self.id)+"]"
  
  
  # Article model represents one article in the blog.
  class Article(models.Model):
      title = models.CharField(max_length=255)
      slug = models.SlugField(max_length=255)
      contents = models.TextField()
      date_published = models.DateTimeField()
      published = models.BooleanField()
      categories = models.ManyToManyField(Category)
      
      def __str__(self):
          return self.title+" ["+str(self.id)+"]"
  
  
  
new_contents: from django.db import models
  
  # Represents a category which articles can be part of
  class Category(models.Model):
      name = models.CharField(max_length=255)
  
      def __str__(self):
          return self.name+" ["+str(self.id)+"]"
  
  
  # Article model represents one article in the blog.
  class Article(models.Model):
      title = models.CharField(max_length=255)
      slug = models.SlugField(max_length=255)
      contents = models.TextField()
      date_published = models.DateTimeField()
      published = models.BooleanField()
      primary_category = models.ForeignKey(Category, related_name='+')
      categories = models.ManyToManyField(Category)
      
      def __str__(self):
          return self.title+" ["+str(self.id)+"]"
  
  
  
subject: Add a primary category which will decide which category is shown as current in the chrome for this article.