docs: def rollback(self):
          """Rollback configuration to filename or to self.rollback_cfg file."""
          filename = self.rollback_cfg
          cfg_file = self._gen_full_path(filename)
          if not self._check_file_exists(cfg_file):
              raise ReplaceConfigException("Rollback config file does not exist")
          cmd = "configure replace {} force".format(cfg_file)
          self.device.send_command_expect(cmd)
  
          # After a rollback - we no longer know whether this is configured or not.
          self.prompt_quiet_configured = None
  
          # Save config to startup
          self.device.save_config()