code: public <V> void observe(Callable<V> callable, CheckedConsumer<V> onSuccess, Consumer<Exception> onFailure) {
          service.executeAsynchronously(wrap(callable, onSuccess, onFailure), config);
      }
docs: Invokes runnable asynchronously with respecting circuit logic and cache
  logic if configured. If callable completed with success then the
  {@code onSuccess} method is called. If callable throws exception then
  {@code onFailure} method is called
  
  @param <V> type of returned value by callable
  @param callable method fired by executor
  @param onSuccess method fired if callable is completed with success
  @param onFailure method fired if callable throws