games is a list of .tfrecord.zz game records.

def parallel_fill(self, games, threads=8):
        """ games is a list of .tfrecord.zz game records. """
        games.sort(key=os.path.basename)
        # A couple extra in case parsing fails
        max_games = int(self.max_size / self.sampling_frac / 200) + 480
        if len(games) > max_games:
            games = games[-max_games:]

        with mp.Pool(threads) as pool:
            res = tqdm(pool.imap(self.func, games), total=len(games))
            self.examples.extend(itertools.chain.from_iterable(res))
        print("Got", len(self.examples), "examples")