docs: private static DistributionValue.BucketOptions toBucketOptionsProto(
        Distribution.BucketOptions bucketOptions) {
      final DistributionValue.BucketOptions.Builder builder =
          DistributionValue.BucketOptions.newBuilder();
      bucketOptions.match(
          new Function<Distribution.BucketOptions.ExplicitOptions, Void>() {
            @Override
            public Void apply(Distribution.BucketOptions.ExplicitOptions arg) {
              builder.setExplicit(
                  DistributionValue.BucketOptions.Explicit.newBuilder()
                      .addAllBounds(arg.getBucketBoundaries())
                      .build());
              return null;
            }
          },
          Functions.<Void>throwAssertionError());
      return builder.build();
    }