@Override
    public CircuitBreakerRpcClientBuilder mapping(CircuitBreakerMapping mapping) {
        return (CircuitBreakerRpcClientBuilder) super.mapping(mapping);
    }
Returns a newly-created decorator that decorates an {@link RpcClient} with a new
{@link CircuitBreakerRpcClient} based on the properties of this builder.
core/src/main/java/com/linecorp/armeria/client/circuitbreaker/CircuitBreakerRpcClientBuilder.java