unescapeChar function
Implementation
int? unescapeChar(String input) {
String unescaped = unescape(input);
if (unescaped.runes.length > 1) throw FormatException("Found mutliple characters ${unescaped.runes.length}!");
if (unescaped.runes.isEmpty) return null;
return unescaped.runes.elementAt(0);
}