code: @Override
    public void write(byte[] buf, int off, int len) throws IOException {
      addBookKeeperEntry(buf, off, len);
    }
docs: Write the buffer to a new entry in a BookKeeper ledger.
  @see OutputStream#write(byte[], int, int)
  @see #addBookKeeperEntry(byte[], int, int)
  @throws IOException If there is an error adding the BookKeeper entry.