    def next_epoch_itr(
        self, shuffle=True, fix_batches_to_gpus=False, set_dataset_epoch=True
    ):
        """Return a new iterator over the dataset.

        Args:
            shuffle (bool, optional): shuffle batches before returning the
                iterator (default: True).
            fix_batches_to_gpus (bool, optional): ensure that batches are always
                allocated to the same shards across epochs. Requires
                that :attr:`dataset` supports prefetching (default: False).
            set_dataset_epoch (bool, optional): update the wrapped Dataset with
                the new epoch number (default: True).
        """
        raise NotImplementedError
Return a new iterator over the dataset.

Args:
shuffle (bool, optional): shuffle batches before returning the
iterator (default: True).
fix_batches_to_gpus (bool, optional): ensure that batches are always
allocated to the same shards across epochs. Requires
that :attr:`dataset` supports prefetching (default: False).
set_dataset_epoch (bool, optional): update the wrapped Dataset with
the new epoch number (default: True).
fairseq/data/iterators.py