def get_hostname(self, server, version, instance=None):
    if server not in self._server_name_to_version_to_hostname:
      raise ServerDoesNotExistError()
    if version not in self._server_name_to_version_to_hostname[server]:
      raise VersionDoesNotExistError()
    if instance:

      raise InvalidInstanceIdError()
    return self._server_name_to_version_to_hostname[server][version]
Returns the hostname for a (server, version, instance) tuple.
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/api/request_info.py/_LocalFakeDispatcher.get_hostname