static <T> RampingUpLoadBalancerBuilder<T> builderForRampingUp(
            Iterable<? extends T> candidates, ToIntFunction<? super T> weightFunction) {
        requireNonNull(candidates, "candidates");
        requireNonNull(weightFunction, "weightFunction");
        //noinspection unchecked
        return new RampingUpLoadBalancerBuilder<>((Iterable<T>) candidates, (ToIntFunction<T>) weightFunction);
    }
Returns a new {@link RampingUpLoadBalancerBuilder} that builds
a {@link LoadBalancer} which ramps up the weight of newly added
candidates. The candidate is selected using weighted random distribution.

@param weightFunction the weight function which returns the weight of the candidate.
core/src/main/java/com/linecorp/armeria/common/loadbalancer/LoadBalancer.java