code: protected function saveMeta()
      {
          foreach ($this->getMetaAttributes() as $attribute) {
              if (is_null($attribute->getValue())) {
                  $attribute->delete();
              } else {
                  $this->metaAttributes()->save($attribute);
              }
          }
      }
docs: Save new or updated meta attributes and delete the ones that were unset.
  
  @return void