code: def create_refresh_token(identity, expires_delta=None, user_claims=None):
      
      jwt_manager = _get_jwt_manager()
      return jwt_manager._create_refresh_token(identity, expires_delta, user_claims)
docs: Creates a new refresh token.
  
      :param identity: The identity of this token, which can be any data that is
                       json serializable. It can also be a python object, in which
                       case you can use the
                       :meth:`~flask_jwt_extended.JWTManager.user_identity_loader`
                       to define a callback function that will be used to pull a
                       json serializable identity out of the object.
      :param expires_delta: A `datetime.timedelta` for how long this token should
                            last before it expires. Set to False to disable
                            expiration. If this is None, it will use the
                            'JWT_REFRESH_TOKEN_EXPIRES` config value
                            (see :ref:`Configuration Options`)
      :param user_claims: Optionnal JSON serializable to override user claims.
      :return: An encoded refresh token