@property<EOL><INDENT>def refresh_token(self):<DEDENT>
return self._refresh_token<EOL>
Gets the refresh_token of this ObtainTokenRequest.
A valid refresh token for generating a new OAuth access token. A valid refresh token is required if `grant_type` is set to `refresh_token` , to indicate the application wants a replacement for an expired OAuth access token.

:return: The refresh_token of this ObtainTokenRequest.
:rtype: str