code: public Retrofit build() {
          checkState(baseUrl != null, "baseUrl not set");
          final URI uri = URI.create(baseUrl);
          final String fullUri = SessionProtocol.of(uri.getScheme()) + "://" + uri.getAuthority();
          final HttpClient baseHttpClient = HttpClient.of(
                  clientFactory, fullUri, configurator.apply(fullUri, new ClientOptionsBuilder()).build());
          return retrofitBuilder.baseUrl(convertToOkHttpUrl(baseHttpClient, uri.getPath(), GROUP_PREFIX))
                                .callFactory(new ArmeriaCallFactory(
                                        baseHttpClient, clientFactory, configurator,
                                        streaming ? SubscriberFactory.streaming(callbackExecutor)
                                                  : SubscriberFactory.blocking()))
                                .build();
      }
docs: Returns a newly-created {@link Retrofit} based on the properties of this builder.