code: func mapJSON(m map[string]interface{}) (string, error) {
  	version, hasVersion := m["camliVersion"]
  	if !hasVersion {
  		return "", ErrNoCamliVersion
  	}
  	delete(m, "camliVersion")
  	jsonBytes, err := json.MarshalIndent(m, "", "  ")
  	if err != nil {
  		return "", err
  	}
  	m["camliVersion"] = version
  	var buf bytes.Buffer
  	fmt.Fprintf(&buf, "{\"camliVersion\": %v,\n", version)
  	buf.Write(jsonBytes[2:])
  	return buf.String(), nil
  }
docs: // JSON returns the map m encoded as JSON in its
  // recommended canonical form. The canonical form is readable with newlines and indentation,
  // and always starts with the header bytes:
  //
  //   {"camliVersion":
  //