test.py

def add_servers(self, servers):
  if not servers:
    return
    self._add_servers_config(servers)
    self._restart_service()

def _add_servers_config(self, servers):
        cfg_parser = Parser(cf_path)
        configuration = cfg_parser.build_configuration()

        backend = configuration.backend('osnodes')

        for server in servers:
            sname = 'web%s' % self._count
            self._count = self._count + 1

            backend.servers().append(config.Server(sname, server[0], server[1], ['check', ]))

        cfg_render = Render(configuration)
        cfg_render.dumps_to(cf_path)