func (i1 Interval) adjacent(i2 Interval) bool {
	return i1.en == i2.st || i2.en == i1.st
}

// MergeInto merges interval i2 into i1. This version happens to
// require that the two intervals either overlap or are adjacent.
func (i1 *Interval) MergeInto(i2 Interval) error {
	if !i1.Overlaps(i2) && !i1.adjacent(i2) {
		return fmt.Errorf("merge method invoked on non-overlapping/non-adjacent")
	}

            return finalizers;
        }
        if (current instanceof OrdinalGroup) {
            return CompositeNodeGroup.mergeInto((OrdinalGroup) current, finalizers);
        } else {
            return CompositeNodeGroup.mergeInto((HasFinalizers) current, finalizers);
        }
    }

    /**
     * Maybe update the group for this node when its dependencies are in groups with higher ordinal.