if self.prediction_mode == "Dense":
            d[self.key_predictions] = DataDefinition([-1, -1, self.prediction_size], [torch.Tensor], "Batch of predictions, each represented as sequence of probability distributions over classes [BATCH_SIZE x SEQ_LEN x PREDICTION_SIZE]")
        elif self.prediction_mode == "Last": # "Last"
            # Only last prediction.
            d[self.key_predictions] = DataDefinition([-1, self.prediction_size], [torch.Tensor], "Batch of predictions, each represented as a single probability distribution over classes [BATCH_SIZE x PREDICTION_SIZE]")