text: from django.contrib import admin
  from django.utils.html import format_html
  from django.urls import reverse
  
  from . import models
  
  
  def related_content_link(obj, related_class, related_field,
                           related_manager='objects', count=None):
      """
      Return a link to the admin changelist for the instances of related_class
      linked to the object.
      """
      url = 'admin:{}_{}_changelist'.format(
          related_class._meta.app_label, related_class._meta.model_name)
      queryset = getattr(related_class, related_manager).filter(
          **{related_field: obj})
      if count is None:
          count = queryset.count()
      return format_html(
          '<a href="{}?{}={}">{}</a>',
          reverse(url), related_field, obj.pk, count)
  
  
  def related_single_content_link(obj, related_field):
      """
      Return a link to the admin change page for a related instance linked to the
      object.
      """
      instance = getattr(obj, related_field)
      if instance:
          related_class = instance._meta.model
          url = 'admin:{}_{}_change'.format(
              related_class._meta.app_label, related_class._meta.model_name)
          return format_html(
              '<a href="{}">{}</a>',
              reverse(url, args=(instance.pk,)), repr(instance))
      else:
          return ''
  
  
  admin.site.register(models.Config)
  admin.site.disable_action('delete_selected')
  