code: def register(app_name, modules):
      
      global INSTALLED_APPS_REGISTER
      mod_list = INSTALLED_APPS_REGISTER.get(app_name, [])
  
      if isinstance(modules, basestring):
          mod_list.append(modules)
      elif is_iterable(modules):
          mod_list.extend(modules)
  
      INSTALLED_APPS_REGISTER[app_name] = mod_list
docs: simple module registering for later usage
      we don't want to import admin.py in models.py