code: def prefixlen_to_mask(prefixlen):
      
      prefixlen = prefixlen or '32'
      addr = '0.0.0.0/%s' % prefixlen
      return str(netaddr.IPNetwork(addr).netmask)
docs: Converts a prefix length to a dotted decimal subnet mask
  
      Args:
          prefixlen (str): The prefix length value to convert
  
      Returns:
          str: The subt mask as a dotted decimal string