code: func getChildService(d *device, serviceType string) *service {
  	for i := range d.ServiceList.Service {
  		if d.ServiceList.Service[i].ServiceType == serviceType {
  			return &d.ServiceList.Service[i]
  		}
  	}
  	return nil
  }
docs: // getChildDevice searches the service list of device for a service with the
  // given type.