code: public void removeTangoUserListener(ITangoUserListener listener, String attrName)
              throws DevFailed {
          synchronized (moni) {
              TangoUser tangoUser;
              String key = deviceName+"/"+attrName;
              if ((tangoUser = tango_user_source.get(key)) != null)
                  tangoUser.removeTangoUserListener(listener);
          }
      }
docs: =======================================================================