code: func ToFileName(name string) string {
  	in := split(name)
  	out := make([]string, 0, len(in))
  
  	for _, w := range in {
  		out = append(out, lower(w))
  	}
  
  	return strings.Join(out, "_")
  }
docs: // ToFileName lowercases and underscores a go type name