code: def pfxmask(scope, ips, pfxlen):
      
      mask = ipv4.pfxlen2mask_int(pfxlen[0])
      return [ipv4.int2ip(ipv4.ip2int(ip) & mask) for ip in ips]
docs: Applies the given prefix length to the given ips, resulting in a
      (list of) IP network addresses.
  
      :type  ips: string
      :param ips: An IP address, or a list of IP addresses.
      :type  pfxlen: int
      :param pfxlen: An IP prefix length.
      :rtype:  string
      :return: The mask(s) that result(s) from converting the prefix length.