/**
  * Create a new SelectableRoute object.
  * 
  * @param boolean $fixed If the SelectableRoute is fixed.
  * @param boolean $required If the SelectableRoutei is required.
  * @param boolean $visible If the SelectableRoute is visible.
  * @param boolean $keepTogether If the SelectableRoute must be kept together.
  */
 public function __construct($fixed = false, $required = false, $visible = true, $keepTogether = true)
 {
     parent::__construct();
     $this->setFixed($fixed);
     $this->setRequired($required);
     $this->setVisible($visible);
     $this->setKeepTogether($keepTogether);
 }