question: public FormIndex stepIndexOut ( FormIndex index ) { if ( index . isTerminal ( ) ) { return null ; } else { return new FormIndex ( stepIndexOut ( index . getNextLevel ( ) ) , index ) ; } }
target:  used to go up one level in the formIndex. That is, if you're at 5_0, 1 (the second question in a repeating group), this method will return a FormInex of 5_0 (the start of the repeating group). If your at index 16 or 5_0, this will return null;