docs: protected static <E extends MTreeEntry, N extends AbstractMTreeNode<?, N, E>> double[][] computeDistanceMatrix(AbstractMTree<?, N, E, ?> tree, N node) {
      final int n = node.getNumEntries();
      double[][] distancematrix = new double[n][n];
      // Build distance matrix
      for(int i = 0; i < n; i++) {
        E ei = node.getEntry(i);
        double[] row_i = distancematrix[i];
        for(int j = i + 1; j < n; j++) {
          row_i[j] = distancematrix[j][i] = tree.distance(ei, node.getEntry(j));
        }
      }
      return distancematrix;
    }