code: def _collate_item(self, item, max_length, pad_id):
      item = self._maybe_cast_to_list(item)
      # max_length = max([len(x) for x in item]) if item else 0
      # here [0] should be tokenizer.pad_id
      item = [x + [pad_id] * (max_length - len(x)) for x in item]
      return item
  
imports: import re
  from typing import List, Mapping, Optional
  import datasets
  import numpy
  import torch
  from datasets import load_dataset
  from nemo.collections.common.tokenizers.tokenizer_spec import TokenizerSpec
  from nemo.collections.nlp.data.language_modeling.megatron.dataset_utils import get_samples_mapping
  from nemo.collections.nlp.data.language_modeling.text_memmap_dataset import JSONLMemMapDataset
  from nemo.core.classes import Dataset
  from nemo.utils import logging
label_desc: Use image node_id 11 for calling the GPTSFTDataset obj's underlying member method code with example usage: obj._collate_item(item, max_length, pad_id) and returns: item