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: category.go
    path of file: ./repos/go-starter-kit/vendor/github.com/olebedev/on/vendor/github.com/codegangsta/cli
    
    the code of the file until where you have to start completion: package cli

type CommandCategories []*CommandCategory

type CommandCategory struct {
	Name     string
	Commands Commands
}

func (c CommandCategories) Less(i, j int) bool {
	return c[i].Name < c[j].Name
}

func (c CommandCategories) Len() i
    
func (c CommandCategories) AddCommand(category string, command Command) CommandCategories {
	for _, commandCategory := range c {
		if commandCategory.Name == category {
			commandCategory.Commands = append(commandCategory.Commands, command)
			return c
		}
	}
	return append(c, &CommandCategory{Name: category, Commands: []Command{command}})
}