code: func (whisper *Whisper) SendP2PMessage(peerID []byte, envelope *Envelope) error {
  	p, err := whisper.getPeer(peerID)
  	if err != nil {
  		return err
  	}
  	return whisper.SendP2PDirect(p, envelope)
  }
docs: // SendP2PMessage sends a peer-to-peer message to a specific peer.