public static double?Sum(this IHistogram histogram, string label) => histogram.Value(label)?.Sum;
public static long?Count(this IHistogram histogram, string label) => histogram.Value(label)?.Count;
public static double Sum(this IHistogram histogram) => histogram.Value().Sum;
public static HistogramBucket Bucket(this IHistogram histogram, double b) => histogram.Value().Buckets.First(bucket => bucket.UpperBound == b);
public static long Count(this IHistogram histogram) => histogram.Value().Count;