+ if (this.needs != null)
+ for(Sequence s : this.needs)
+ (s.needed==null?(s.needed=new HashSet<Sequence>()):s.needed).add(this);
+ if (this.hates != null)
+ for(Sequence s : this.hates)
+ (s.hated==null?(s.hated=new HashSet<Sequence>()):s.hated).add(this);