old_contents: # coding=utf-8
  """
  Logical permission backends module
  """
  __author__ = 'Alisue <lambdalisue@hashnote.net>'
  __all__ = ('LogicalPermissionBackend',)
  from permission.utils.handlers import registry
  
  
  class PermissionBackend(object):
      """
      A handler based permission backend
      """
      supports_object_permissions = True
      supports_anonymous_user = True
      supports_inactive_user = True
  
      def authenticate(self, username, password):
          """
          Always return ``None`` to prevent authentication within this backend.
          """
          return None
  
      def has_perm(self, user_obj, perm, obj=None):
          """
          Check if user have permission (of object) based on registered handlers.
  
          Parameters
          ----------
          user_obj : django user model instance
              A django user model instance which be checked
          perm : string
              `app_label.codename` formatted permission string
          obj : None or django model instance
              None or django model instance for object permission
  
          Returns
          -------
          boolean
              Wheter the specified user have specified permission (of specified
              object).
          """
          # get permission handlers fot this perm
          cache_name = '_%s_cache' % perm
          if hasattr(self, cache_name):
              handlers = getattr(self, cache_name)
          else:
              handlers = [h for h in registry.get_handlers()
                          if perm in h.get_permissions(user_obj, perm, obj=obj)]
              setattr(self, cache_name, handlers)
          for handler in handlers:
              if handler.has_perm(user_obj, perm, obj=obj):
                  return True
          return False
  
new_contents: # coding=utf-8
  """
  Logical permission backends module
  """
  __author__ = 'Alisue <lambdalisue@hashnote.net>'
  __all__ = ('PermissionBackend',)
  from permission.utils.handlers import registry
  
  
  class PermissionBackend(object):
      """
      A handler based permission backend
      """
      supports_object_permissions = True
      supports_anonymous_user = True
      supports_inactive_user = True
  
      def authenticate(self, username, password):
          """
          Always return ``None`` to prevent authentication within this backend.
          """
          return None
  
      def has_perm(self, user_obj, perm, obj=None):
          """
          Check if user have permission (of object) based on registered handlers.
  
          Parameters
          ----------
          user_obj : django user model instance
              A django user model instance which be checked
          perm : string
              `app_label.codename` formatted permission string
          obj : None or django model instance
              None or django model instance for object permission
  
          Returns
          -------
          boolean
              Wheter the specified user have specified permission (of specified
              object).
          """
          # get permission handlers fot this perm
          cache_name = '_%s_cache' % perm
          if hasattr(self, cache_name):
              handlers = getattr(self, cache_name)
          else:
              handlers = [h for h in registry.get_handlers()
                          if perm in h.get_permissions(user_obj, perm, obj=obj)]
              setattr(self, cache_name, handlers)
          for handler in handlers:
              if handler.has_perm(user_obj, perm, obj=obj):
                  return True
          return False
  
subject: Fix __all__