docs: def save(filename=None, family='ipv4'):
      '''
      Save the current in-memory rules to disk
  
      CLI Example:
  
      .. code-block:: bash
  
          salt '*' nftables.save /etc/nftables
      '''
      if _conf() and not filename:
          filename = _conf()
  
      nft_families = ['ip', 'ip6', 'arp', 'bridge']
      rules = "#! nft -f\n"
      for family in nft_families:
          out = get_rules(family)
          if out:
              rules += '\n'
          rules = rules + '\n'.join(out)
      rules = rules + '\n'
  
      try:
          with salt.utils.files.fopen(filename, 'wb') as _fh:
              # Write out any changes
              _fh.writelines(salt.utils.data.encode(rules))
      except (IOError, OSError) as exc:
          raise CommandExecutionError(
              'Problem writing to configuration file: {0}'.format(exc)
          )
      return rules