code: public function getModules($loadedOnly = false)
      {
          if ($loadedOnly) {
              $modules = [];
              foreach ($this->_modules as $module) {
                  if ($module instanceof self) {
                      $modules[] = $module;
                  }
              }
  
              return $modules;
          }
  
          return $this->_modules;
      }
docs: Returns the sub-modules in this module.
  @param bool $loadedOnly whether to return the loaded sub-modules only. If this is set `false`,
  then all sub-modules registered in this module will be returned, whether they are loaded or not.
  Loaded modules will be returned as objects, while unloaded modules as configuration arrays.
  @return array the modules (indexed by their IDs).