def save_client_creds(self, client_token):
raise NotImplementedError<EOL>
Save the Client token in a file. This is used by the SSH server
to store the client credentails if credentials are delegated
(server mode).

:param str client_token: The SSPI token received form the client
:raises:
    ``NotImplementedError`` -- Credential delegation is currently not
    supported in server mode