docs: public String findFilter(String destination) {
          FindFilterEvent event = new FindFilterEvent();
          event.setDestination(destination);
          try {
              Object obj = delegate.callManager(event);
              if (obj != null && obj instanceof String) {
                  return (String) obj;
              } else {
                  throw new CanalException("No Such Canal by [" + destination + "]");
              }
          } catch (Exception e) {
              throw new CanalException("call_manager_error", e);
          }
      }