code: @Override
    public void writeHeader(RandomAccessFile file) throws IOException {
      super.writeHeader(file);
      file.writeInt(min_fanout);
      file.writeLong(num_elements);
      file.writeInt(dimensionality);
      file.writeFloat(max_overlap);
      file.writeLong(supernode_offset);
    }
docs: Writes this header to the specified file. Writes to file the integer values
  <code>version</code>, <code>pageSize</code>, {@link #dirCapacity},
  {@link #leafCapacity}, {@link #dirMinimum}, {@link #leafMinimum},
  {@link #min_fanout}, {@link #dimensionality}, the <code>float</code>
  {@link #max_overlap} and the
  <code>long</code> {@link #supernode_offset}.