code: func (n Network) Masked(ones int) Network {
  	mask := net.CIDRMask(ones, len(n.Number)*BitsPerUint32)
  	return NewNetwork(net.IPNet{
  		IP:   n.IP.Mask(mask),
  		Mask: mask,
  	})
  }
docs: // Masked returns a new network conforming to new mask.