bucketsLock sync.Mutex
	buckets     []string
}

// NewMetricsGroup creates a new MetricsGroup. To create a metrics group for
// metrics with a `bucket` dimension (label), use `NewBucketMetricsGroup`.
//
// The `loader` function loads metrics from the cache and the system.
func NewMetricsGroup(path collectorPath, descriptors []MetricDescriptor,
	loader MetricsLoaderFn,
) *MetricsGroup {