code: func ToWhisperMessage(message *ReceivedMessage) *Message {
  	msg := Message{
  		Payload:   message.Payload,
  		Padding:   message.Padding,
  		Timestamp: message.Sent,
  		TTL:       message.TTL,
  		PoW:       message.PoW,
  		Hash:      message.EnvelopeHash.Bytes(),
  		Topic:     message.Topic,
  	}
  
  	if message.Dst != nil {
  		b := crypto.FromECDSAPub(message.Dst)
  		if b != nil {
  			msg.Dst = b
  		}
  	}
  
  	if isMessageSigned(message.Raw[0]) {
  		b := crypto.FromECDSAPub(message.SigToPubKey())
  		if b != nil {
  			msg.Sig = b
  		}
  	}
  
  	return &msg
  }
docs: // ToWhisperMessage converts an internal message into an API version.