code: def prepend_bos_token(label, bos_index):
      """Create labels with <bos> token at the beginning.
  
      Arguments
      ---------
      label : torch.IntTensor
          Containing the original labels. Must be of size: [batch_size, max_length].
      bos_index : int
          The index for <bos> token.
  
      Returns
      -------
      new_label : tensor
          The new label with <bos> at the beginning.
  
      Example
      -------
      >>> label=torch.LongTensor([[1,0,0], [2,3,0], [4,5,6]])
      >>> new_label=prepend_bos_token(label, bos_index=7)
      >>> new_label
      tensor([[7, 1, 0, 0],
              [7, 2, 3, 0],
              [7, 4, 5, 6]])
      """
      new_label = label.long().clone()
      batch_size = label.shape[0]
  
      bos = new_label.new_zeros(batch_size, 1).fill_(bos_index)
      new_label = torch.cat([bos, new_label], dim=1)
      return new_label
  
imports: import os
  import torch
  import logging
  import numpy
  import pickle
  import hashlib
  import csv
  import time
  import torchaudio
  import json
  import re
  from speechbrain.utils.torch_audio_backend import check_torchaudio_backend
label_desc: Use image node_id 22 for calling a global function with example usage: prepend_bos_token(label, bos_index) and returns: new_label