code: public static <O> RKNNQuery<O> getRKNNQuery(Relation<O> relation, DistanceFunction<? super O> distanceFunction, Object... hints) {
      final DistanceQuery<O> distanceQuery = relation.getDistanceQuery(distanceFunction, hints);
      return relation.getRKNNQuery(distanceQuery, hints);
    }
docs: Get a rKNN query object for the given distance function.
  
  When possible, this will use an index, but it may default to an expensive
  linear scan.
  
  Hints include:
  <ul>
  <li>Integer: maximum value for k needed</li>
  <li>{@link de.lmu.ifi.dbs.elki.database.query.DatabaseQuery#HINT_BULK} bulk
  query needed</li>
  </ul>
  
  @param relation Relation used
  @param distanceFunction Distance function
  @param hints Optimizer hints
  
  @param <O> Object type
  @return RKNN Query object