code: def shift_one(seq, left_pad_num, right_pad_num, pad):
      assert seq.ndim == 1
      bos = seq.new_full((left_pad_num,), pad)
      eos = seq.new_full((right_pad_num,), pad)
      seq = torch.cat([bos, seq, eos])
      mask = torch.ones_like(seq).bool()
      mask[left_pad_num : len(seq) - right_pad_num] = 0
      return seq, mask
  
imports: import json
  import logging
  import os
  import random
  from pathlib import Path
  import numpy
  import torch
  import torch.utils.data
  from .None import data_utils
  from fairseq.data.fairseq_dataset import FairseqDataset
label_desc: Use image node_id 4 for calling the Shifts obj's underlying member method code with example usage: obj.shift_one(seq, left_pad_num, right_pad_num, pad) and returns: seq,  mask