def _set_comment(self, section, comment, key=None):
        """
        Set a comment for section or key

        :param str section: Section to add comment to
        :param str comment: Comment to add
        :param str key: Key to add comment to
        """

        if '\n' in comment:
            comment = '\n# '.join(comment.split('\n'))
        comment = '# ' + comment

        if key:
            self._comments[(section, key)] = comment
        else:
            self._comments[section] = comment