def to_string(self, encoding='utf-8', **kwargs):
        if self.tree is None:
            return ""
        method = self._output_method
        out = etree.tostring(self.tree, encoding=encoding, method=method, **kwargs).decode(encoding)
        if method == 'xml':
            out = self._cdata_regex.sub(
                lambda m: m.group(1) % '/*<![CDATA[*/%s/*]]>*/',
                out
            )
            # Remove empty "<title/>" which breaks html rendering (Fixes #43)
            out = self._xml_title_regex.sub('', out)
        return out
dataset/ETHPy150Open lavr/python-emails/emails/transformer.py/HTMLParser.to_string/swapped operands of `%`