def METHOD_NAME(self):
    """If the authorization server issued a refresh token to the client, the
    client makes a refresh request to the token endpoint by adding the
    following parameters using the "application/x-www-form-urlencoded"
    format per Appendix B with a character encoding of UTF-8 in the HTTP
    request entity-body, per Section 6:
    grant_type
         REQUIRED.  Value MUST be set to "refresh_token".
    refresh_token
         REQUIRED.  The refresh token issued to the client.
    scope
         OPTIONAL.  The scope of the access request as described by
         Section 3.3.  The requested scope MUST NOT include any scope
         not originally granted by the resource owner, and if omitted is
         treated as equal to the scope originally granted by the
         resource owner.
    For example, the client makes the following HTTP request using
    transport-layer security (with extra line breaks for display purposes
    only):
    .. code-block:: http
        POST /token HTTP/1.1
        Host: server.example.com
        Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
        Content-Type: application/x-www-form-urlencoded
        grant_type=refresh_token&refresh_token=tGzv3JOkF0XG5Qx2TlKWIA
    """
    client = self._validate_request_client()
    self.request.client = client
    refresh_token = self._validate_request_token(client)
    self._validate_token_scope(refresh_token)
    self.request.refresh_token = refresh_token