Extends the expiration time of a valid OAuth access token. See
        <https://developers.facebook.com/docs/facebook-login/access-tokens/
        expiration-and-extension>

def extend_access_token(self, app_id, app_secret):
        """
        Extends the expiration time of a valid OAuth access token. See
        <https://developers.facebook.com/docs/facebook-login/access-tokens/
        expiration-and-extension>

        """
        args = {
            "client_id": app_id,
            "client_secret": app_secret,
            "grant_type": "fb_exchange_token",
            "fb_exchange_token": self.access_token,
        }

        return self.request(
            "{0}/oauth/access_token".format(self.version), args=args
        )