docs: @VisibleForTesting
    static BucketOptions createBucketOptions(
        @javax.annotation.Nullable
            io.opencensus.metrics.export.Distribution.BucketOptions bucketOptions) {
      final BucketOptions.Builder builder = BucketOptions.newBuilder();
      if (bucketOptions == null) {
        return builder.build();
      }
  
      return bucketOptions.match(
          bucketOptionsExplicitFunction, Functions.<BucketOptions>throwIllegalArgumentException());
    }