/**
  * Define optional properties.
  */
 protected function optional()
 {
     return array_merge(parent::optional(), array('preferredStartingPosition'));
 }
 /**
  * Define optional properties.
  */
 protected function optional()
 {
     return array_merge(parent::optional(), array('initialAlpha', 'userControllable'));
 }
 /**
  * Define optional properties.
  */
 protected function optional()
 {
     return array_merge(parent::optional(), array('initialAlpha', 'initialScale'));
 }