code: def add_subreddit(self, subreddit, _delete=False, *args, **kwargs):
          
          subreddit = six.text_type(subreddit)
          url = self.reddit_session.config['multireddit_add'].format(
              user=self._author, multi=self.name, subreddit=subreddit)
          method = 'DELETE' if _delete else 'PUT'
          # The modhash isn't necessary for OAuth requests
          if not self.reddit_session._use_oauth:
              self.reddit_session.http.headers['x-modhash'] = \
                  self.reddit_session.modhash
          data = {'model': dumps({'name': subreddit})}
          try:
              self.reddit_session.request(url, data=data, method=method,
                                          *args, **kwargs)
          finally:
              # The modhash isn't necessary for OAuth requests
              if not self.reddit_session._use_oauth:
                  del self.reddit_session.http.headers['x-modhash']
docs: Add a subreddit to the multireddit.
  
          :param subreddit: The subreddit name or Subreddit object to add
  
          The additional parameters are passed directly into
          :meth:`~praw.__init__.BaseReddit.request_json`.