code: func (m *MessageService) SendMessage(from string, to string, body string, mediaURLs []*url.URL) (*Message, error) {
  	v := url.Values{
  		"Body": []string{body},
  		"From": []string{from},
  		"To":   []string{to},
  	}
  	if mediaURLs != nil {
  		for _, mediaURL := range mediaURLs {
  			v.Add("MediaUrl", mediaURL.String())
  		}
  	}
  	return m.Create(context.Background(), v)
  }
docs: // SendMessage is a convenience wrapper around Create.