code: public void removeTangoChangeListener(ITangoChangeListener listener, String attrName)
              throws DevFailed {
          synchronized (moni) {
              TangoChange tangoChange;
              String key = deviceName+"/"+attrName;
              if ((tangoChange = tango_change_source.get(key)) != null)
                  tangoChange.removeTangoChangeListener(listener);
          }
      }
docs: =======================================================================