code: public void addTangoInterfaceChangeListener(ITangoInterfaceChangeListener listener, String deviceName, boolean stateless)
              throws DevFailed {
          TangoInterfaceChange interfaceChange;
          if ((interfaceChange = tango_interface_change_source.get(deviceName)) == null) {
              interfaceChange = new TangoInterfaceChange(deviceProxy);
              tango_interface_change_source.put(deviceName, interfaceChange);
          }
          synchronized (moni) {
              interfaceChange.addTangoInterfaceChangeListener(listener, stateless);
          }
      }
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