code: func (s SourceFilesystems) StaticFs(lang string) afero.Fs {
  	var staticFs afero.Fs = hugofs.NoOpFs
  
  	if fs, ok := s.Static[lang]; ok {
  		staticFs = fs.Fs
  	} else if fs, ok := s.Static[""]; ok {
  		staticFs = fs.Fs
  	}
  
  	return staticFs
  }
docs: // StaticFs returns the static filesystem for the given language.
  // This can be a composite filesystem.