'Validate that the file has not expired based on the I{duration}.
@param fn: The file name.
@type fn: str'

def validate(self, fn):

    if (self.duration[1] < 1):
        return
    created = dt.fromtimestamp(os.path.getctime(fn))
    d = {self.duration[0]: self.duration[1]}
    expired = (created + timedelta(**d))
    if (expired < dt.now()):
        log.debug('%s    expired,    deleted', fn)
        os.remove(fn)
