code: def select_buffer(buffer, batch_slot, count):
      """Util function to select the relevent subpart of a buffer for a given
      batch_slot and batch size"""
      if buffer is None:
          return None
      if isinstance(buffer, tuple):
          return tuple(
              select_buffer(x, batch_slot, count) for x in buffer
          )
  
      return buffer[batch_slot][:count]
  
file_path: ffcv/ffcv/loader/epoch_iterator.py
imports: from collections import defaultdict
  from threading import Thread, Event
  from queue import Queue, Full
  from contextlib import nullcontext
  from typing import Sequence, TYPE_CHECKING
  import torch
  from ..traversal_order.quasi_random import QuasiRandom
  from ..utils import chunks
  from ..pipeline.compiler import Compiler
label_desc: Use image node_id 1 for calling a global function with example usage: select_buffer(buffer, batch_slot, count) and returns: buffer, None, tuple