code: @Override
  	public void updateProperty(String key, String value) {
  	    if (config instanceof ConcurrentCompositeConfiguration) {
  	        ((ConcurrentCompositeConfiguration) config).setOverrideProperty(key, value);
  	    } else {
  		    config.setProperty(key, value);
  	    }
  	}
docs: Calls <code>config.setProperty()</code>. If the underlying configuration
  is {@link ConcurrentCompositeConfiguration}, it calls {@link ConcurrentCompositeConfiguration#setOverrideProperty(String, Object)}
  instead.