code: func (cs Set) Project() string {
  	domain, target, _ := cs.Split()
  	if domain == "projects" {
  		return target
  	}
  	return ""
  }
docs: // Project returns a project name for a project-rooted config set or empty
  // string for all other sets.
  //
  // Use ProjectAndRef if you need to get both the project name and the ref.