presto-main/src/main/java/io/prestosql/type/setdigest/SetDigestFunctions.java/SetDigestFunctions/hashCounts
class SetDigestFunctions:    @ScalarFunction
    @SqlType(StandardTypes.VARCHAR)
    public static Slice hashCounts(@SqlType(SetDigestType.NAME) Slice slice)
    {
        SetDigest digest = SetDigest.newInstance(slice);

        try {
            return Slices.utf8Slice(OBJECT_MAPPER.writeValueAsString(digest.getHashCounts()));
        }
        catch (JsonProcessingException e) {
            throw new UncheckedIOException(e);
        }
    }