return None if v is None else v.strip()
+def url_or_none(url):
+ if not url or not isinstance(url, compat_str):
+ return None
+ url = url.strip()
+ return url if re.match(r'^(?:[a-zA-Z][\da-zA-Z.+-]*:)?//', url) else None
+
+
def parse_duration(s):
if not isinstance(s, compat_basestring):
return None