def rate_limit(function):
        """Return a decorator that enforces API request limit guidelines.

        We are allowed to make a API request every api_request_delay seconds as
        specified in praw.ini. This value may differ from reddit to reddit. For
        reddit.com it is 2. Any function decorated with this will be forced to
        delay _rate_delay seconds from the calling of the last function
        decorated with this before executing.

        This decorator must be applied to a RateLimitHandler class method or
        instance method as it assumes `rl_lock` and `last_call` are available.

        """
        @wraps(function)
        def wrapped(cls, _rate_domain, _rate_delay, **kwargs):
            cls.rl_lock.acquire()
            lock_last = cls.last_call.setdefault(_rate_domain, [Lock(), 0])
            with lock_last[0]:  # Obtain the domain specific lock
                cls.rl_lock.release()
                # Sleep if necessary, then perform the request
                now = timer()
                delay = lock_last[1] + _rate_delay - now
                if delay > 0:
                    now += delay
                    time.sleep(delay)
                lock_last[1] = now
                return function(cls, **kwargs)
        return wrapped