code: public static void setAttributeExhibitable(Boolean isExhibit) {
  		final Preferences prefs = Preferences.userNodeForPackage(BusLayerConstants.class);
  		if (prefs != null) {
  			if (isExhibit == null) {
  				prefs.remove("EXHIBIT_ATTRIBUTES"); //$NON-NLS-1$
  			} else {
  				prefs.putBoolean("EXHIBIT_ATTRIBUTES", isExhibit.booleanValue()); //$NON-NLS-1$
  			}
  			try {
  				prefs.sync();
  			} catch (BackingStoreException exception) {
  				//
  			}
  		}
  	}
docs: Set if the attributes of the bus network elements
  should be exhibited by the layers that are displaying
  them.
  For example, a BusLineLayer may exhibit the BusLine
  attributes.
  
  @param isExhibit is <code>true</code> if the attributes are exhibited by the layers;
  <code>false</code> if the attributes are not exhibited; or <code>null</code>
  if the default value must be restored.