code: def _load_chunk(self, chunk_index: int, chunk_filepath: str) -> None:
      if chunk_index in self._mmaps:
          return
      chunk = self._chunks[chunk_index]
  
      # Skip the header
      # The number of items + the number of offsets (number of items in the chunk + 1)
      # multiplied by the header encoding dtype (np.uint32)
      offset = (1 + chunk["chunk_size"] + 1) * 4
      mmap = np.memmap(
          chunk_filepath, mode="r", order="C", offset=offset
      )
      self._mmaps[chunk_index] = mmap
      self._buffers[chunk_index] = memoryview(mmap)
  
imports: import os
  from abc import ABC, abstractmethod
  from time import sleep
  from typing import Any, Dict, List, Optional, Tuple
  import numpy
  import torch
  from lightning.data.streaming.constants import _TORCH_DTYPES_MAPPING, _TORCH_GREATER_EQUAL_2_1_0
  from lightning.data.streaming.serializers import Serializer
label_desc: Use image node_id 5 for calling the TokensLoader obj's underlying member method code with example usage: obj._load_chunk(chunk_index, chunk_filepath) without return types