code: private function getMediaIdentifiers($values)
      {
          $identifiers = [];
          
          foreach ($values as $key => $id) {
              if (is_int($key)) {
                  $identifiers[] = $id;
              }
          }
          
          return $identifiers;
      }
docs: Fetch only media identifiers from an array
  
  @param array $values
  
  @return array