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: tag_list.go
    path of file: ./repos/restic/internal/restic
    
    the code of the file until where you have to start completion: package restic

import (
	"fmt"
	"strings"
)

// TagList is a list of tags.
type TagList []string

// splitTagList splits a string into a list of tags. The tags in the strin
    
func (l TagLists) Flatten() (tags TagList) {
	tags = make([]string, 0)
	for _, list := range l {
		for _, tag := range list {
			if tag != "" {
				tags = append(tags, tag)
			}
		}
	}

	return tags
}