code: func (l *Netlist) UnmarshalTOML(fn func(interface{}) error) error {
  	var masks []string
  	if err := fn(&masks); err != nil {
  		return err
  	}
  	for _, mask := range masks {
  		_, n, err := net.ParseCIDR(mask)
  		if err != nil {
  			return err
  		}
  		*l = append(*l, *n)
  	}
  	return nil
  }
docs: // UnmarshalTOML implements toml.UnmarshalerRec.