docs: private boolean isParent(Relation<V> relation, Cluster<SubspaceModel> parent, It<Cluster<SubspaceModel>> iter, int db_dim) {
      Subspace s_p = parent.getModel().getSubspace();
      NumberVector parent_centroid = ProjectedCentroid.make(s_p.getDimensions(), relation, parent.getIDs());
      int subspaceDim_parent = db_dim - s_p.dimensionality();
  
      for(; iter.valid(); iter.advance()) {
        Cluster<SubspaceModel> child = iter.get();
        Subspace s_c = child.getModel().getSubspace();
        NumberVector child_centroid = ProjectedCentroid.make(s_c.getDimensions(), relation, child.getIDs());
        long[] commonPreferenceVector = BitsUtil.andCMin(s_p.getDimensions(), s_c.getDimensions());
        int subspaceDim = subspaceDimensionality(parent_centroid, child_centroid, s_p.getDimensions(), s_c.getDimensions(), commonPreferenceVector);
        if(subspaceDim == subspaceDim_parent) {
          return true;
        }
      }
      return false;
    }