code: public static ModifiableDBIDs randomSampleExcept(DBIDs source, DBIDRef except, int k, RandomFactory rnd) {
      return randomSampleExcept(source, except, k, rnd.getSingleThreadedRandom());
    }
docs: Produce a random sample of the given DBIDs.
  
  @param source Original DBIDs, no duplicates allowed
  @param except Excluded object
  @param k k Parameter
  @param rnd Random generator
  @return new DBIDs