Doctrine\Search\Mapping\ClassMetadata::__sleep PHP Method

    public function __sleep()
    {
        // This metadata is always serialized/cached.
        return array('boost', 'className', 'fieldMappings', 'parameters', 'index', 'numberOfReplicas', 'numberOfShards', 'parent', 'timeToLive', 'type', 'value', 'identifier', 'rootMappings');
    }