+
+ # This does not use has/getattr intentionally - we want to know whether
+ # we have cached the regexp for *this* class, whereas getattr would also
+ # match the superclass
+ if '_VALID_URL_RE' not in cls.__dict__:
+ cls._VALID_URL_RE = re.compile(cls._VALID_URL)
+ return cls._VALID_URL_RE.match(url) is not None