code: private function handleCollections(Parameters $params, array $permitted = array())
      {
          // if is empty, any value is allowed
          if (empty($permitted)) {
              return;
          }
  
          $keys = $params->keys();
          $intKeys = $keys->select(function ($value) {
              return is_int($value);
          });
  
          if ($keys->count() === $intKeys->count()) {
              foreach ($keys as $key) {
                  $value = $params[$key];
  
                  if ($value instanceof Parameters) {
                      $this->filter($value, $permitted);
                  }
              }
          }
      }
docs: Handle Parameters that have only integer indexes
  @param Parameter $params
  @param array     $permitted