public Set<String> getContigNames() {
   final TreeSet<String> contigs = new TreeSet<String>();
   for (final SAMSequenceRecord r :
       getToolkit()
           .getReferenceDataSource()
           .getReference()
           .getSequenceDictionary()
           .getSequences()) {
     contigs.add(r.getSequenceName());
   }
   return contigs;
 }