code: def apply_post_filters(instance, html):
      
      for post_func in appsettings.POST_FILTER_FUNCTIONS:
          html = post_func(instance, html)
  
      return html
docs: Allow post processing functions to change the text.
      This change is not saved in the original text.
  
      :type instance: fluent_contents.models.ContentItem
      :raise ValidationError: when one of the filters detects a problem.