How to use the fasteners._utils.RetryAgain function in fasteners

def _try_acquire(self, blocking, watch):
        try:
            self.trylock()
        except IOError as e:
            if e.errno in (errno.EACCES, errno.EAGAIN):
                if not blocking or watch.expired():
                    return False
                else:
                    raise _utils.RetryAgain()
            else:
                raise threading.ThreadError("Unable to acquire lock on"
                                            " `%(path)s` due to"
                                            " %(exception)s" %
                                            {
                                                'path': self.path,
                                                'exception': e,
                                            })
        else:
            return True

def __call__(self, fn, *args, **kwargs):
        while True:
            self.attempts += 1
            try:
                return fn(*args, **kwargs)
            except RetryAgain:
                maybe_delay = self.attempts * self.delay
                if maybe_delay < self.max_delay:
                    actual_delay = maybe_delay
                else:
                    actual_delay = self.max_delay
                actual_delay = max(0.0, actual_delay)
                if self.watch is not None:
                    leftover = self.watch.leftover()
                    if leftover is not None and leftover < actual_delay:
                        actual_delay = leftover
                self.sleep_func(actual_delay)