docs: public void attachSession(List<ServiceInstanceToken> instanceTokens, final AttachSessionCallback cb, Object context){
          ProtocolHeader header = new ProtocolHeader();
          header.setType(ProtocolType.AttachSession);
  
          String sessionId = connection.getSessionId();
          AttachSessionProtocol protocol = new AttachSessionProtocol(instanceTokens, sessionId);
          ProtocolCallback pcb = new ProtocolCallback(){
  
              @Override
              public void call(boolean result, Response response,
                      ErrorCode error, Object ctx) {
                  Map<ServiceInstanceToken, ItemResult> items = ((AttachSessionResponse)response).getAttachingResult();
                  cb.call(result, items, error, ctx);
              }
  
          };
  
          connection.submitCallbackRequest(header, protocol, pcb, context);
      }