code: def is_meta_url (attr, attrs):
      
      res = False
      if attr == "content":
          equiv = attrs.get_true('http-equiv', u'').lower()
          scheme = attrs.get_true('scheme', u'').lower()
          res = equiv in (u'refresh',) or scheme in (u'dcterms.uri',)
      if attr == "href":
          rel = attrs.get_true('rel', u'').lower()
          res = rel in (u'shortcut icon', u'icon')
      return res
docs: Check if the meta attributes contain a URL.