code: func (i *Invoice) Send(b *Bot, to Recipient, opt *SendOptions) (*Message, error) {
  	prices, _ := json.Marshal(i.Prices)
  
  	params := map[string]string{
  		"chat_id":         to.Recipient(),
  		"title":           i.Title,
  		"description":     i.Description,
  		"start_parameter": i.Start,
  		"payload":         i.Payload,
  		"provider_token":  i.Token,
  		"currency":        i.Currency,
  		"prices":          string(prices),
  	}
  	embedSendOptions(params, opt)
  
  	respJSON, err := b.Raw("sendInvoice", params)
  	if err != nil {
  		return nil, err
  	}
  
  	return extractMsgResponse(respJSON)
  }
docs: // Send delivers media through bot b to recipient.