code: def get_user_tweets(self, auth_secret, username, max_cnt_tweets):
          
          result = {pytwis_constants.ERROR_KEY: None}
  
          # Check if the user is logged in.
          loggedin, _ = self._is_loggedin(auth_secret)
          if not loggedin:
              result[pytwis_constants.ERROR_KEY] = pytwis_constants.ERROR_NOT_LOGGED_IN
              return (False, result)
  
          # Get the userid from the username.
          userid = self._rc.hget(pytwis_constants.USERS_KEY, username)
          if userid is None:
              result[pytwis_constants.ERROR_KEY] = \
                  pytwis_constants.ERROR_USERNAME_NOT_EXIST_FORMAT.format(username)
              return (False, result)
  
          # Get the tweets posted by the user.
          user_tweets_key = pytwis_constants.USER_TWEETS_KEY_FORMAT.format(userid)
  
          result[pytwis_constants.TWEETS_KEY] = \
              self._get_tweets(user_tweets_key, max_cnt_tweets)
          return (True, result)
docs: Get the tweets posted by one user.
  
          Parameters
          ----------
          auth_secret: str
              The authentication secret of the logged-in user.
          username:
              The name of the user who post the tweets and may not be the logged-in user.
          max_cnt_tweets: int
              The maximum number of tweets included in the return. If it is set to -1,
              then all the tweets posted by the user will be included.
  
          Returns
          -------
          bool
              True if the tweets are successfully retrieved, False otherwise.
          result
              A dict containing a list of tweets with the key TWEETS_KEY if
              the tweets are successfully retrieved, a dict containing
              the error string with the key ERROR_KEY otherwise.
  
          Note
          ----
          Possible error strings are listed as below:
  
          -  ERROR_NOT_LOGGED_IN
          -  ERROR_USERNAME_NOT_EXIST_FORMAT.format(username)