code: public function save(ModelInterface $objItem, $timestamp = null)
      {
          if (null === $timestamp) {
              // @codingStandardsIgnoreStart
              @\trigger_error(
                  'Not passing a timestamp has been deprecated and will cause an error in MetaModels 3',
                  E_USER_DEPRECATED
              );
              // @codingStandardsIgnoreEnd
          }
  
          if ($objItem instanceof Model) {
              $backupLanguage = $this->setLanguage($this->getCurrentLanguage());
  
              $objItem->getItem()->save($timestamp);
  
              $this->setLanguage($backupLanguage);
  
              return $objItem;
          }
  
          throw new \RuntimeException('ERROR: incompatible object passed to GeneralDataMetaModel::save()');
      }
docs: Save an item to the data provider.
  
  If the item does not have an Id yet, the save operation will add it as a new row to the database and
  populate the Id of the model accordingly.
  
  @param ModelInterface $objItem   The model to save back.
  
  @param int|null            $timestamp Optional the timestamp.
  
  @return ModelInterface The passed model.
  
  @throws \RuntimeException When an incompatible item was passed, an Exception is being thrown.