code: public static String unescape(String input, char echar, char[] allowEscaped) {
          return unescape(input, echar, allowEscaped, new char[0]).unescaped;
      }
docs: Unescape the input string by removing the escape char for allowed chars
  
  @param input        input string
  @param echar        escape char
  @param allowEscaped all chars that can be escaped by the escape char
  
  @return unescaped string