def auth(self):
if self.private_token or self.oauth_token:<EOL><INDENT>self._token_auth()<EOL><DEDENT>else:<EOL><INDENT>self._credentials_auth()<EOL><DEDENT>
Performs an authentication.

        Uses either the private token, or the email/password pair.

        The `user` attribute will hold a `gitlab.objects.CurrentUser` object on
        success.