code: public <V> V invoke(Callable<V> callable) throws Exception {
          return service.executeSynchronously(callable, config);
      }
docs: Invokes callable synchronously with respecting circuit logic and cache
  logic if configured.
  
  @param <V> type of value returned by this method
  @param callable method fired by executor
  @return {@code V} returns value returned by callable
  @throws Exception if callable throws some exception