code: def mask(scope, ips, mask):
      
      mask = ipv4.ip2int(mask[0])
      return [ipv4.int2ip(ipv4.ip2int(ip) & mask) for ip in ips]
docs: Applies the given IP mask (e.g. 255.255.255.0) to the given IP address
      (or list of IP addresses) and returns it.
  
      :type  ips: string
      :param ips: A prefix, or a list of IP prefixes.
      :type  mask: string
      :param mask: An IP mask.
      :rtype:  string
      :return: The network(s) that result(s) from applying the mask.