outgoing.go
func (ov *OutgoingVoice) querystring() querystring {
	toReturn := map[string]string(ov.getBaseQueryString())

	if ov.Duration != 0 {
		toReturn["duration"] = fmt.Sprint(ov.Duration)
	}

	return querystring(toReturn)
}
func (ov *OutgoingVoice) querystring() querystring {
	toReturn := map[string]string(ov.getBaseQueryString())

	if ov.Duration != 0 {
		toReturn["duration"] = fmt.Sprint(ov.Duration)
	}

	return querystring(toReturn)
}
// querystring implements querystringer to represent the outgoing voice
// note.