Index domain with certain indices without mentioning separate set

Hi,

I am trying to write a constraint with index domain on certain indices

vBinary1('1') + vBinary1('3') + vBinary1('5') = 3 * vBinary2;

‘h’ is the index. Here ‘h’ is taking value {‘1’, ‘3’, ‘5’}. Do not consider it as ODD. 

I tried with 

```

index domain: | h in {"1", "3", "5"} 

sum[h, vBinary1(h)] = 3 * vBinary2;

```

It is giving errors by saying 

The scope of index "h" has not been specified. Help to understand it. 

Do not define another set for these indices only. That I know how to do it.