code: def check_anchor(self, url_data):
          
          log.debug(LOG_PLUGIN, "checking anchor %r in %s", url_data.anchor, self.anchors)
          enc = lambda anchor: urlutil.url_quote_part(anchor, encoding=url_data.encoding)
          if any(x for x in self.anchors if enc(x[0]) == url_data.anchor):
              return
          if self.anchors:
              anchornames = sorted(set(u"`%s'" % x[0] for x in self.anchors))
              anchors = u", ".join(anchornames)
          else:
              anchors = u"-"
          args = {"name": url_data.anchor, "anchors": anchors}
          msg = u"%s %s" % (_("Anchor `%(name)s' not found.") % args,
                            _("Available anchors: %(anchors)s.") % args)
          url_data.add_warning(msg)
docs: If URL is valid, parseable and has an anchor, check it.
          A warning is logged and True is returned if the anchor is not found.