docs: public static ProjectedCentroid make(long[] dims, Relation<? extends NumberVector> relation, DBIDs ids) {
      ProjectedCentroid c = new ProjectedCentroid(dims, RelationUtil.dimensionality(relation));
      for(DBIDIter iter = ids.iter(); iter.valid(); iter.advance()) {
        c.put(relation.get(iter));
      }
      return c;
    }