examples/legacy/seq2seq/utils.py/DistributedSortishSampler/available_indices
class DistributedSortishSampler:    def available_indices(self) -> np.array:
        indices = list(range(len(self.dataset)))
        # add extra samples to make it evenly divisible
        indices += indices[: (self.total_size - len(indices))]
        assert len(indices) == self.total_size
        # subsample
        available_indices = indices[self.rank : self.total_size : self.num_replicas]
        return available_indices