You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: config.go
    path of file: ./repos/minio/internal/event
    
    the code of the file until where you have to start completion: // Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object
    
func (s3Key S3Key) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	if s3Key.RuleList.isEmpty() {
		return nil
	}
	type s3KeyWrapper S3Key
	return e.EncodeElement(s3KeyWrapper(s3Key), start)
}