func (r *Reporter) Flush() error {
	r.log(strings.Join(r.metrics, " "))
	r.metrics = r.metrics[:0]
	return nil
}
func (r *Reporter) Flush() error {
	r.log(strings.Join(r.metrics, " "))
	r.metrics = r.metrics[:0]
	return nil
}
// Flush implements instruments.Reporter