@Override
    public byte[] serializeValue(CoordinatorRecord record) {
        // Tombstone is represented with a null value.
        if (record.value() == null) {
            return null;
        } else {
            return MessageUtil.toVersionPrefixedBytes(
                record.value().version(),
                record.value().message()
            );
        }
    }
@Test
    public void testSerializeNullValue() {
        GroupCoordinatorRecordSerde serializer = new GroupCoordinatorRecordSerde();
        CoordinatorRecord record = new CoordinatorRecord(
            new ApiMessageAndVersion(
                new ConsumerGroupMetadataKey().setGroupId("group"),
                (short) 1
            ),
            null
        );

        assertNull(serializer.serializeValue(record));
    }