def set_epoch(self, epoch):
        """Sets the epoch number for the underlying sampler which ensures all replicas
        to use a different ordering for each epoch.

        Only available when :attr:`use_ddp` is True.

        Calls :meth:`torch.utils.data.distributed.DistributedSampler.set_epoch`.

        Parameters
        ----------
        epoch : int
            The epoch number.
        """
        if self.use_ddp:
            self.dist_sampler.set_epoch(epoch)
        else:
            raise DGLError("set_epoch is only available when use_ddp is True.")
Sets the epoch number for the underlying sampler which ensures all replicas
        to use a different ordering for each epoch.

        Only available when :attr:`use_ddp` is True.

        Calls :meth:`torch.utils.data.distributed.DistributedSampler.set_epoch`.

        Parameters
        ----------
        epoch : int
            The epoch number.
        
python/dgl/dataloading/dataloader.py