private Set < Tuple > getOnceTupleDefs ( final List < VarDef > combinedVars ) { try { return new HashSet < Tuple > ( IteratorUtils . toList ( IteratorUtils . transformedIterator ( getOnceTuples ( ) , tupleRef -> toTuple ( combinedVars , tupleRef ) ) ) ) ; } catch ( Exception e ) { throw new IllegalStateException ( "Invalid once-only tuple definition" , e ) ; } }
Returns the set of once - only tuple definitions for this combiner .