uid4 function
Implementation
String uid4([int? repeat]) {
repeat ??= 1;
final sb = StringBuffer();
for (var i = 0; i < repeat; ++i) {
sb.write(((Random().nextDouble() + 1) * 0x10000)
.truncate()
.toRadixString(16)
.substring(1));
}
return sb.toString();
}