/**
* Return an instance of this class.
*
* @since 1.0.0
* @return object A single instance of this class.
*/
public static function get_instance($parent = null)
{
// If the single instance hasn't been set, set it now.
if (null == self::$instance) {
self::$instance = new self();
}
if ($parent !== null) {
self::$instance->parent = $parent;
}
return self::$instance;
}
