class_docstr: 用于读取 **conll2003** 任务的数据。数据的内容应该类似于以下的内容：第一列为 **raw_words** ，第二列为 **pos** ，
  第三列为 **chunking** ，第四列为 **ner** 。
  数据中以 ``"-DOCSTART-"`` 开头的行将被忽略，因为该符号在 **conll2003** 中被用为文档分割符。
  
  Example::
  
      Nadim NNP B-NP B-PER
      Ladki NNP I-NP I-PER
  
      AL-AIN NNP B-NP B-LOC
      United NNP B-NP B-LOC
      Arab NNP I-NP I-LOC
      Emirates NNPS I-NP I-LOC
      1996-12-06 CD I-NP O
      ...
  
  读取的 :class:`~fastNLP.core.DataSet` 将具备以下的数据结构：
  
  .. csv-table:: 下面是 Conll2003Loader 加载后数据具备的结构。
     :header: "raw_words", "pos", "chunk", "ner"
  
     "[Nadim, Ladki]", "[NNP, NNP]", "[B-NP, I-NP]", "[B-PER, I-PER]"
     "[AL-AIN, United, Arab, ...]", "[NNP, NNP, NNP, ...]", "[B-NP, B-NP, I-NP, ...]", "[B-LOC, B-LOC, I-LOC, ...]"
     "[...]", "[...]", "[...]", "[...]"
class_docstr_tok: ["\u7528\u4e8e\u8bfb\u53d6","*","*","conll2003","*","*","\u4efb\u52a1\u7684\u6570\u636e\u3002\u6570\u636e\u7684\u5185\u5bb9\u5e94\u8be5\u7c7b\u4f3c\u4e8e\u4ee5\u4e0b\u7684\u5185\u5bb9\uff1a\u7b2c\u4e00\u5217\u4e3a","*","*","raw_words","*","*","\uff0c\u7b2c\u4e8c\u5217\u4e3a","*","*","pos","*","*","\uff0c","\u7b2c\u4e09\u5217\u4e3a","*","*","chunking","*","*","\uff0c\u7b2c\u56db\u5217\u4e3a","*","*","ner","*","*","\u3002","\u6570\u636e\u4e2d\u4ee5","``","``","-DOCSTART-","''","``","\u5f00\u5934\u7684\u884c\u5c06\u88ab\u5ffd\u7565\uff0c\u56e0\u4e3a\u8be5\u7b26\u53f7\u5728","*","*","conll2003","*","*","\u4e2d\u88ab\u7528\u4e3a\u6587\u6863\u5206\u5272\u7b26\u3002","Example",":",":","Nadim","NNP","B-NP","B-PER","Ladki","NNP","I-NP","I-PER","AL-AIN","NNP","B-NP","B-LOC","United","NNP","B-NP","B-LOC","Arab","NNP","I-NP","I-LOC","Emirates","NNPS","I-NP","I-LOC","1996-12-06","CD","I-NP","O","...","\u8bfb\u53d6\u7684",":","class",":","`","~fastNLP.core.DataSet","`","\u5c06\u5177\u5907\u4ee5\u4e0b\u7684\u6570\u636e\u7ed3\u6784\uff1a","..","csv-table",":",":","\u4e0b\u9762\u662f","Conll2003Loader","\u52a0\u8f7d\u540e\u6570\u636e\u5177\u5907\u7684\u7ed3\u6784\u3002",":","header",":","``","raw_words","''",",","``","pos","''",",","``","chunk","''",",","``","ner","''","``","[","Nadim",",","Ladki","]","''",",","``","[","NNP",",","NNP","]","''",",","``","[","B-NP",",","I-NP","]","''",",","``","[","B-PER",",","I-PER","]","''","``","[","AL-AIN",",","United",",","Arab",",","...","]","''",",","``","[","NNP",",","NNP",",","NNP",",","...","]","''",",","``","[","B-NP",",","B-NP",",","I-NP",",","...","]","''",",","``","[","B-LOC",",","B-LOC",",","I-LOC",",","...","]","''","``","[","...","]","''",",","``","[","...","]","''",",","``","[","...","]","''",",","``","[","...","]","''"]
code: def download(self, output_dir=None):
      raise RuntimeError(
          "conll2003 cannot be downloaded automatically."
      )
  
imports: import glob
  import os
  import random
  import shutil
  import time
  from typing import List
  from .loader import Loader
  from ..file_reader import _read_conll
  from fastNLP.core.dataset import DataSet, Instance
label_desc: Use image node_id 3 for calling the Conll2003Loader obj's underlying member method code with example usage: obj.download(output_dir) without return types