code: def check(self, url_data):
          
          log.debug(LOG_PLUGIN, "checking content for warning regex")
          content = url_data.get_content()
          # add warnings for found matches, up to the maximum allowed number
          match = self.warningregex.search(content)
          if match:
              # calculate line number for match
              line = content.count('\n', 0, match.start())
              # add a warning message
              msg = _("Found %(match)r at line %(line)d in link contents.")
              url_data.add_warning(msg % {"match": match.group(), "line": line})
docs: Check content.