class_docstr: **QNLI** 数据集的 **Loader** ，如果您的实验使用到了该数据，请引用
  
      https://arxiv.org/pdf/1809.05053.pdf
      
  读取数据的格式为：第一行为标题（具体内容会被忽略），之后每一行是一个 sample，由 **index** 、**问题** 、**句子** 和 **标签** 构成（以制表符分割），数据结构如下::
  
      index   question        sentence        label
      0       What came into force after the new constitution was herald?     As of that day, the new constitution heralding the Second Republic came into force.     entailment
  
  加载的 :class:`~fastNLP.core.DataSet` 将具备以下的内容： ``raw_words1`` 是 ``question`` ， ``raw_words2`` 是 ``sentence`` ， ``target`` 是 ``label`` 。
  测试集中没有 ``target`` 列。
  
  .. csv-table::
      :header: "raw_words1", "raw_words2", "target"
  
      "What came into force after the new...", "As of that day...", "entailment"
      "...","."
docstr: 自动下载数据集。
  
  :return: 数据集目录地址
docstr_tok: ["\u81ea\u52a8\u4e0b\u8f7d\u6570\u636e\u96c6\u3002",":","return",":","\u6570\u636e\u96c6\u76ee\u5f55\u5730\u5740"]
code: def download(self):
      r"""
      自动下载数据集。
  
      :return: 数据集目录地址
      """
      return self._get_dataset_path("qnli")
  
imports: import os
  from typing import Union, Dict
  from .csv import CSVLoader
  from .json import JsonLoader
  from .loader import Loader
  from fastNLP.io.data_bundle import DataBundle
  from ..utils import check_loader_paths
  from fastNLP.core.dataset import DataSet, Instance
  from fastNLP.core.log import logger
label_desc: Use image node_id 3 for calling the QNLILoader obj's underlying member method code with example usage: obj.download() and returns: self