docs: def _backup_bytes(target, offset, length):
      """
          Read bytes from one file and write it to a
          backup file with the .bytes_backup suffix
      """
      click.echo('Backup {l} byes at position {offset} on file {file} to .bytes_backup'.format(
          l=length, offset=offset, file=target))
  
      with open(target, 'r+b') as f:
          f.seek(offset)
  
          with open(target + '.bytes_backup', 'w+b') as b:
              for _ in xrange(length):
                  byte = f.read(1)
                  b.write(byte)
              b.flush()
  
          f.flush()