code: def prepare_refresh_body(self, body='', refresh_token=None, scope=None, **kwargs):
          
          refresh_token = refresh_token or self.refresh_token
          return prepare_token_request(self.refresh_token_key, body=body, scope=scope,
                                       refresh_token=refresh_token, **kwargs)
docs: Prepare an access token request, using a refresh token.
  
          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 in the HTTP request entity-body:
  
          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.