code: public Observable<HttpClientResponse<O>> submit(final HttpClientRequest<I> request, final RetryHandler errorHandler, final IClientConfig requestConfig) {
          return submit(null, request, errorHandler, requestConfig, null);
      }
docs: Submit a request to server chosen by the load balancer to execute. An error will be emitted from the returned {@link Observable} if
  there is no server available from load balancer.
  
  @param errorHandler A handler to determine the load balancer retry logic. If null, the default one will be used.
  @param requestConfig An {@link IClientConfig} to override the default configuration for the client. Can be null.
  @return