docs: def random_model(ctx, model_class_name):
      """
      Get a random model identifier by class name. For example::
  
          # db/fixtures/Category.yml
          {% for i in range(0, 10) %}
          category{{ i }}:
              name: {{ faker.name() }}
          {% endfor %}
  
          # db/fixtures/Post.yml
          a_blog_post:
              category: {{ random_model('Category') }}
  
      Will render to something like the following::
  
          # db/fixtures/Post.yml (rendered)
          a blog_post:
              category: "Category(category7)"
  
      :param ctx: The context variables of the current template (passed automatically)
      :param model_class_name: The class name of the model to get.
      """
      model_identifiers = ctx['model_identifiers'][model_class_name]
      if not model_identifiers:
          return 'None'
      idx = random.randrange(0, len(model_identifiers))
      return '"%s(%s)"' % (model_class_name, model_identifiers[idx])