code: public ResponseOnSingeRequest onComplete(Response response) {
  
          cancelCancellable();
          try {
              
              Map<String, List<String>> responseHeaders = null;
              if (responseHeaderMeta != null) {
                  responseHeaders = new LinkedHashMap<String, List<String>>();
                  if (responseHeaderMeta.isGetAll()) {
                      for (Map.Entry<String, List<String>> header : response
                              .getHeaders()) {
                          responseHeaders.put(header.getKey().toLowerCase(Locale.ROOT), header.getValue());
                      }
                  } else {
                      for (String key : responseHeaderMeta.getKeys()) {
                          if (response.getHeaders().containsKey(key)) {
                              responseHeaders.put(key.toLowerCase(Locale.ROOT),
                                      response.getHeaders().get(key));
                          }
                      }
                  }
              }
  
              int statusCodeInt = response.getStatusCode();
              String statusCode = statusCodeInt + " " + response.getStatusText();
              String charset = ParallecGlobalConfig.httpResponseBodyCharsetUsesResponseContentType &&
                      response.getContentType()!=null ? 
                      AsyncHttpProviderUtils.parseCharset(response.getContentType())
                      : ParallecGlobalConfig.httpResponseBodyDefaultCharset;
              if(charset == null){
                  getLogger().error("charset is not provided from response content type. Use default");
                  charset = ParallecGlobalConfig.httpResponseBodyDefaultCharset; 
              }
              reply(response.getResponseBody(charset), false, null, null, statusCode,
                      statusCodeInt, responseHeaders);
          } catch (IOException e) {
              getLogger().error("fail response.getResponseBody " + e);
          }
  
          return null;
      }
docs: On complete.
  Save response headers when needed.
  
  @param response
  the response
  @return the response on single request