def ordered_indices(self):
        """Return an ordered list of indices. Batches will be constructed based
        on this order."""
        if self.shuffle:
            indices = np.random.permutation(len(self))
        else:
            indices = np.arange(len(self))
        if self.tgt_sizes is not None:
            indices = indices[np.argsort(self.tgt_sizes[indices], kind='mergesort')]
        return indices[np.argsort(self.src_sizes[indices], kind='mergesort')]
Return an ordered list of indices. Batches will be constructed based
        on this order.
infoxlm/fairseq/fairseq/data/language_pair_dataset.py