code: protected function _normalizeConfig($orders)
      {
          if (empty($orders)) {
              $orders = [[]];
          } elseif (isset($orders['order']) || isset($orders['callback'])) {
              $orders = [$orders];
          }
  
          $default = [
              'order' => $this->_table->aliasField($this->_table->getDisplayField()),
              'callback' => null,
          ];
  
          foreach ($orders as $key => $value) {
              $orders[$key] = $orders[$key] + $default;
          }
  
          $this->_config = [
              'orders' => $orders,
          ];
      }
docs: Normalize configuration.
  
  @param mixed $orders Orders config
  @return void