@Contract(pure = true)
  public static @NotNull String unescapeChar(@NotNull String str, char unescapeChar) {
    StringBuilder buf = new StringBuilder(str.length());
    unescapeChar(buf, str, unescapeChar);
    return buf.toString();
  }
@Contract(pure = true)
  public static @NotNull String unescapeChar(@NotNull String str, char unescapeChar)