def check(self, url_data):
        """Check content."""
        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})
Check content.