code: def list_extensions(request):
      
      blacklist = set(getattr(settings,
                              'OPENSTACK_NOVA_EXTENSIONS_BLACKLIST', []))
      nova_api = _nova.novaclient(request)
      return tuple(
          extension for extension in
          nova_list_extensions.ListExtManager(nova_api).show_all()
          if extension.name not in blacklist
      )
docs: List all nova extensions, except the ones in the blacklist.