docs: def rel_to_abs(self, base_url):
          """
          Converts relative links from html contents to absolute links
          """
          # Delete target attributes
          strip_attributes(self.tree, 'target')
  
          # Absolute links
          self.tree.rewrite_links(
              lambda link: urljoin(base_url, link)
              if not link.startswith(self.rel_to_abs_excluded_prefixes) else link)
  
          # Extra attributes
          onclick_elements = self.tree.xpath('//*[@onclick]')
  
          for element in onclick_elements:
              # Replace attribute with absolute URL
              element.set('onclick', self.javascript_open_re.sub(
                  lambda match: '%s%s%s' % (match.group('opening'),
                          urljoin(base_url, match.group('url')),
                          match.group('ending')),
                  element.get('onclick')))