docs: def user_exists(self, username):
          """
          Returns whether a user with username ``username`` exists.
  
          :param str username: username of user
          :return: whether a user with the specified username exists
          :rtype: bool
          :raises NetworkFailure: if there is an error communicating with the server
          :return:
          """
          path = "/users/{}".format(username)
          return self._get(path).ok