public static function initModulesHierarchy()
 {
     if (!empty(self::$modulesByLevels)) {
         return true;
     }
     include 'user_privileges/moduleHierarchy.php';
     self::$modulesHierarchy = $modulesHierarchy;
     self::$modulesMapRelatedFields = $modulesMapRelatedFields;
     foreach (self::$modulesHierarchy as $module => &$details) {
         if (vtlib_isModuleActive($module)) {
             self::$modulesByLevels[$details['level']][$module] = $details;
         }
     }
 }