Bolt\Storage\Query\ContentQueryParser::getIdentifier PHP Method

    public function getIdentifier()
    {
        return $this->identifier;
    }

 /**
  * @param ContentQueryParser $contentQuery
  *
  * @return mixed
  */
 public function __invoke(ContentQueryParser $contentQuery)
 {
     if (is_numeric($contentQuery->getIdentifier())) {
         $contentQuery->setParameter('id', $contentQuery->getIdentifier());
     } else {
         $contentQuery->setParameter('slug', $contentQuery->getIdentifier());
     }
     if (count($contentQuery->getContentTypes()) === 1) {
         $contentQuery->setDirective('returnsingle', true);
     }
     return call_user_func_array($contentQuery->getHandler('select'), [$contentQuery]);
 }