def update_user(self, user_name, new_user_name=None, new_path=None):
        """
        Updates name and/or path of the specified user.

        :type user_name: string
        :param user_name: The name of the user

        :type new_user_name: string
        :param new_user_name: If provided, the username of the user will be
                              changed to this username.

        :type new_path: string
        :param new_path: If provided, the path of the user will be
                         changed to this path.

        """
        params = {'UserName' : user_name}
        if new_user_name:
            params['NewUserName'] = new_user_name
        if new_path:
            params['NewPath'] = new_path
        return self.get_response('UpdateUser', params)