public static RetryDecision retry(Backoff backoff) {
        if (backoff == Backoff.ofDefault()) {
            return DEFAULT;
        }
        return new RetryDecision(requireNonNull(backoff, "backoff"));
    }
Returns a {@link RetryDecision} that retries with the specified {@link Backoff}.
core/src/main/java/com/linecorp/armeria/client/retry/RetryDecision.java