presto-cassandra/src/main/java/io/prestosql/plugin/cassandra/CassandraPageSink.java/CassandraPageSink/finish
class CassandraPageSink:    @Override
    public CompletableFuture<Collection<Slice>> finish()
    {
        // the committer does not need any additional info
        return completedFuture(ImmutableList.of());
    }