def __init__(self, url=None, valid_since=None):
        """`url` should be a unicode object or utf8 encoded str (will be decoded 
        automatically).
        
        `valid_since` is a datetime.datetime object, it's the first time Pipl's
        crawlers found this data on the page.
        
        """
        Field.__init__(self, valid_since)
        self.url = url
def __init__ ( self , url = None , valid_since = None ) : Field . __init__ ( self , valid_since ) self . url = url
`url` should be a unicode object or utf8 encoded str (will be decoded 
        automatically).
        
        `valid_since` is a datetime.datetime object, it's the first time Pipl's
        crawlers found this data on the page.