func (r *RatioCounter) Reset() {
	r.a.Reset()
	r.b.Reset()
}
Reset reset the counter
package memmetrics
import (
	"time"
	"github.com/mailgun/timetools"
)
type ratioOptSetter func(r *RatioCounter) error
func RatioClock(clock timetools.TimeProvider) ratioOptSetter {
	return func(r *RatioCounter) error {
		r.clock = clock
		return nil
	}
}
type RatioCounter struct {
	clock timetools.TimeProvider
	a     *RollingCounter
	b     *RollingCounter
}
func NewRatioCounter(buckets int, resolution time.Duration, options ...ratioOptSetter) (*RatioCounter, error) {
	rc := &RatioCounter{}
	for _, o := range options {
		if err := o(rc); err != nil {
			return nil, err
		}
	}
	if rc.clock == nil {
		rc.clock = &timetools.RealTime{}
	}
	a, err := NewCounter(buckets, resolution, CounterClock(rc.clock))
	if err != nil {
		return nil, err
	}
	b, err := NewCounter(buckets, resolution, CounterClock(rc.clock))
	if err != nil {
		return nil, err
	}
	rc.a = a
	rc.b = b
	return rc, nil
}