code: def update_shortlink(self, shortlink_id, callback_uri=None,
                           description=None):
          
          arguments = {'callback_uri': callback_uri,
                       'description': description}
          return self.do_req('PUT',
                             self.merchant_api_base_url + '/shortlink/' +
                             shortlink_id + '/', arguments)
docs: Update existing shortlink registration
  
          Arguments:
              shortlink_id:
                  Shortlink id assigned by mCASH