code: func GetServerID(o dhcp6.Options) (DUID, error) {
  	v, err := o.GetOne(dhcp6.OptionServerID)
  	if err != nil {
  		return nil, err
  	}
  
  	return parseDUID(v)
  }
docs: // GetServerID returns the Server Identifier Option value, as described in RFC
  // 3315, Section 22.3.
  //
  // The DUID returned allows unique identification of a server to a client.