code: def fetch_request_token(self, url, realm=None, **request_kwargs):
          r
          self._client.client.realm = " ".join(realm) if realm else None
          token = self._fetch_token(url, **request_kwargs)
          log.debug("Resetting callback_uri and realm (not needed in next phase).")
          self._client.client.callback_uri = None
          self._client.client.realm = None
          return token
docs: r"""Fetch a request token.
  
          This is the first step in the OAuth 1 workflow. A request token is
          obtained by making a signed post request to url. The token is then
          parsed from the application/x-www-form-urlencoded response and ready
          to be used to construct an authorization url.
  
          :param url: The request token endpoint URL.
          :param realm: A list of realms to request access to.
          :param \*\*request_kwargs: Optional arguments passed to ''post''
          function in ''requests.Session''
          :returns: The response in dict format.
  
          Note that a previously set callback_uri will be reset for your
          convenience, or else signature creation will be incorrect on
          consecutive requests.
  
          >>> request_token_url = 'https://api.twitter.com/oauth/request_token'
          >>> oauth_session = OAuth1Session('client-key', client_secret='secret')
          >>> oauth_session.fetch_request_token(request_token_url)
          {
              'oauth_token': 'sdf0o9823sjdfsdf',
              'oauth_token_secret': '2kjshdfp92i34asdasd',
          }