code: public void addTangoAttConfigListener(ITangoAttConfigListener listener, String attrName, String[] filters, boolean stateless)
              throws DevFailed {
          TangoAttConfig tangoAttConfig;
          String key = deviceName+"/"+attrName;
          if ((tangoAttConfig = tango_att_config_source.get(key)) == null) {
              tangoAttConfig = new TangoAttConfig(deviceProxy, attrName, filters);
              tango_att_config_source.put(key, tangoAttConfig);
          }
  
          synchronized (moni) {
              tangoAttConfig.addTangoAttConfigListener(listener, stateless);
          }
      }
docs: =======================================================================