class_docstr: 实现一个简单的迭代器来模拟实际的 dataloader，从给定的 ``dataloader`` 中取出部分数据，来让 Trainer 实现 overfit 的功能；
class_docstr_tok: ["\u5b9e\u73b0\u4e00\u4e2a\u7b80\u5355\u7684\u8fed\u4ee3\u5668\u6765\u6a21\u62df\u5b9e\u9645\u7684","dataloader\uff0c\u4ece\u7ed9\u5b9a\u7684","``","dataloader","``","\u4e2d\u53d6\u51fa\u90e8\u5206\u6570\u636e\uff0c\u6765\u8ba9","Trainer","\u5b9e\u73b0","overfit","\u7684\u529f\u80fd\uff1b"]
code: def __getattr__(self, item):
      return getattr(self.dataloader, item)
  
file_path: fastNLP/fastNLP/core/dataloaders/utils.py
imports: import os
  from typing import Callable, Any, Union, Sequence
  from abc import ABC
  import inspect
  import ast
  from ..log import logger
  from ..utils.cache_results import get_func_calls, truncate_start_blanks
label_desc: Use image node_id 4 for calling the OverfitDataLoader obj's underlying member method code with example usage: obj.__getattr__(item) and returns: getattr