docs: def rel_to_abs(self, base_url):
          """
          Converts relative links from css contents to absolute links
  
          :param base_url: The base page url to use for building absolute links
          :type base_url: str
          :param css_contents: The CSS contents to parse
          :type css_contents: str
          """
          self.cleaned_css = self.rel_to_abs_re.sub(
              lambda match: "url('%s')" % urljoin(
                  base_url, match.group('path').strip('\'"')),
              self.cleaned_css)