Splits of data to produce and number the output shards for each.

def dataset_splits(self):
    """Splits of data to produce and number the output shards for each."""
    return [{
        "split": problem.DatasetSplit.TRAIN,
        "shards": self.num_train_shards,
    }, {
        "split": problem.DatasetSplit.EVAL,
        "shards": self.num_eval_shards,
    }, {
        "split": problem.DatasetSplit.TEST,
        "shards": self.num_test_shards,
    }]