code: def request_access_token(self, params):
          
          return self.request(self.access_token_url, method="POST", params=params,
              is_signed=False)
docs: Request the access token from `self.access_token_url`. The default 
          behaviour is to use a `POST` request, but some services use `GET` 
          requests. Individual clients can override this method to use the 
          correct HTTP method.