docs: def _post_tidy(html):
      """ This method transforms post tidy. Will go away when tidy goes away. """
      tree = etree.fromstring(html)
      ems = tree.xpath(
          "//xh:em[@class='underline']|//xh:em[contains(@class, ' underline ')]",
          namespaces={'xh': 'http://www.w3.org/1999/xhtml'})
      for el in ems:
          c = el.attrib.get('class', '').split()
          c.remove('underline')
          el.tag = '{http://www.w3.org/1999/xhtml}u'
          if c:
              el.attrib['class'] = ' '.join(c)
          elif 'class' in el.attrib:
              del(el.attrib['class'])
  
      return tree