public static @Nullable String getStringError(String fragmentText) {
    if (fragmentText.startsWith("\\") && fragmentText.length() > 1 && !VALID_ESCAPE.matcher(fragmentText).matches()) {
      if (fragmentText.startsWith("\\u")) {
        return JsonBundle.message("syntax.error.illegal.unicode.escape.sequence");
      }
      else {
        return JsonBundle.message("syntax.error.illegal.escape.sequence");
      }
    }
    return null;
  }
public static @Nullable String getStringError(String fragmentText)