public SortedSet<Literal> getCompleteBackbone() {
        final SortedSet<Literal> completeBackbone = new TreeSet<>();
        if (hasPositiveBackboneResult()) {
            completeBackbone.addAll(this.positiveBackbone);
        }
        if (hasNegativeBackboneResult()) {
            for (final Variable var : this.negativeBackbone) {
                completeBackbone.add(var.negate());
            }
        }
        return Collections.unmodifiableSortedSet(completeBackbone);
    }
public SortedSet < Literal > getCompleteBackbone ( ) { final SortedSet < Literal > completeBackbone = new TreeSet < > ( ) ; if ( hasPositiveBackboneResult ( ) ) { completeBackbone . addAll ( this . positiveBackbone ) ; } if ( hasNegativeBackboneResult ( ) ) { for ( final Variable var : this . negativeBackbone ) { completeBackbone . add ( var . negate ( ) ) ; } } return Collections . unmodifiableSortedSet ( completeBackbone ) ; }
Returns all literals of the backbone.  Positive backbone variables have positive polarity, negative
backbone variables have negative polarity.
@return the set of both positive and negative backbone variables as literals